One plant of five showing leaf problems

Hi, first time grower here. Been lurking for a while, but finally have a reason to post.

I've got 5 plants growing in a tent and they've all been treated exactly the same. However, one of them is showing some leaf problems, particularly the lower leaves, while the other four plants are looking great. Here are the stats on the problematic plant:

Strain: White Widow (ILGM)
Location: Indoor
Soil: FFOF/Perlite (70/30) in 5 gal fabric pots. Transplanted into this pot 18 days ago
Soil pH: 6.5-6.6
Temp: 73-81F
RH: 60-70%
Water stats: Well water tap. Very clean, pH usually around 6.6-6.7, TDS always 120-130ppm. Let rest to room temperature before watering
Water schedule: wet/dry schedule, every few days at this point. I wait until the top few inches are dry and I don't see any condensation between the fabric pot and the plastic tray.
Stage: Vegetative (47 days old from sprout)
Feeding: Not feeding anything yet since they're barely 2 weeks into fresh FFOF soil. The other 4 plants show no signs of deficiency under same conditions.

Problem: Lower leaves increasingly yellowing, mottled browning. Growth has stunted a bit in the last week. The other plants are almost twice its size by now.
Diagnosing: So far, I've taken a soil sample from a few inches down and did a slurry test. It came back at a solid 6.6 pH. I haven't yet done a runoff test, I'll do that when I water it again in a day or two.
Other observations: It's mostly affected some of the lower leaves, but I'm starting to see early signs on some higher up. New growth seems to look OK enough. All other plants are thriving under the same conditions and schedules. The stunted growth is particularly worrisome.

Based on what I've been reading, and since the soil pH is in the right range, it looked like it could be a calcium deficiency. I went ahead and gave it a light dose of Cal-Mag (around 200ppm) on 10/29, but it seems to have continued getting worse through today.

I've attached three photos showing the progression from 10/27-10/31. Sorry about the 10/27 pic, it was a wider shot from the webcam, before I took any close-up shots after noticing the problem, but it's good enough to see the difference in color.

Any advice would be helpful!

Updated pics attached. The leaves shown initially have gotten worse, though I don't expect them to recover once the problem is solved. I included a wider shot of the plant here as well as a shot showing some of the other plants, which look darker and more healthy. The new growth and upper sections look decent enough, but compared to the rest of the plants in the tent, it's definitely a much lighter green than the rest, even on the healthier parts. I'm baffled at this point since the other plants are doing so well with the exact same treatment. This one remains more stunted than the rest, which are growing nicely. They were all topped 3 or 4 days ago and are growing out as expected, including this problematic one (albeit a bit slower).

I haven't done much and am trying to take a light touch with it since the pH stats check out. Still not feeding them since they're in fairly new FFOF, but I did give them a little Big Bloom on the last watering, 2Tbsp/gallon. Total PPM was around 380 (tap is 120ish) and everyone still seems pretty happy except this one. The yellowing leaves make me inclined to thing she's hungry and I've got veg nutes ready to go once the FFOF is depleted, but given that the others are fine, I'm afraid I'll end up just burning her if that's not the actual problem.

Any ideas or guidance would be helpful!

Are you fully watering those, and waiting for them to dry out? Soil looks very dry in most of the pics
They shouldnt show any deficiencies in ffof for some time, most times its alittle hot in the beginning

The pics in the first post I'd taken over a couple of days between watering. For the bottom ones, the close up shots were taken just after watering all of them with about a half-gallon each with some runoff taking place, and the wide tent shot was snapped from the webcam earlier today (so a day after they were watered). Generally, they've been watered once the top few inches of soil are dry and the pots start to feel light, but before they start drooping. I do try and let them dry as much as is reasonable before watering again, but not until they're drooping if I can avoid it (though it's happened once or twice)

Thanks for the confirmation that they shouldn't be showing any deficiencies this quickly in ffof. I did test the soil pH in this one the other day, but I forgot to collect runoff for a pH test when I watered them yesterday. I plan to do that on the next watering to confirm pH levels lower in the soil.

rf25532 said:

The pics in the first post I'd taken over a couple of days between watering. For the bottom ones, the close up shots were taken just after watering all of them with about a half-gallon each with some runoff taking place, and the wide tent shot was snapped from the webcam earlier today (so a day after they were watered). Generally, they've been watered once the top few inches of soil are dry and the pots start to feel light, but before they start drooping. I do try and let them dry as much as is reasonable before watering again, but not until they're drooping if I can avoid it (though it's happened once or twice)

Thanks for the confirmation that they shouldn't be showing any deficiencies this quickly in ffof. I did test the soil pH in this one the other day, but I forgot to collect runoff for a pH test when I watered them yesterday. I plan to do that on the next watering to confirm pH levels lower in the soil.

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It is mass produced soil..
If the other plants are fine.. It may just be a weak one

It's not just that one, all your girls look to have some type of issue. I wouldn't stress it too much. At that size in a 5 gal fabric, I water like once every 7-8 days. Yellowing tips is usually the tell sign of something, which I'm seeing on yours. Could be alot of things.

Calcium … semi mobile element . Typical mottled brown spotting .
Your water source ( well ) may be lacking compared to municipal water sources. There are various ways to supplement.

Calcium ( cal mag )
Kelp or Kelp meal ( BTW would be good for ALL of your plants ) and can be Foliar sprayed too.
Garden Lime / Gypsum amendment.

Calmag at a “ maintenance “ amount ( see label ) would be the easiest .

Yeah, I attributed the yellowing tips on these to the hotter FFOF soil. They started showing up in the week after transplant from the starter soil, but didn't seem to go much further than the tips. Since then, they've all maintained a decent color, though I notice some of the newer growth looks lighter in color than the older growth, but maybe that's normal.

I can definitely start adding a small amount of cal-mag with each watering for the next couple of weeks to see if that helps. I'll check the label for the maintenance amount. My well water is about 120ppm out of the tap, so maybe that's just a bit too low to keep up appropriate levels.

Regarding lime, I did actually add some to the soil before planting to help keep it buffered. Fresh out of the bag, I tested the FFOF soil (slurry test) and it came in at around 5.9 pH (which was disappointing), so that's why I added the lime. So far, subsequent slurry tests have shown the soil to be around 6.6.

I suppose it's also possible that this one plant is just a weaker one. Hopefully some regular cal-mag will help her to perk back up.

I watered them last night with a solid dose of Cal-Mag (1tsp/gallon). It went in at about a pH of 6.7 and 440ppm. I collected the first runoff of this problematic plant and the pH of the runoff was 6.0 at about 850ppm. I collected some runoff from one of the healthier plants and got the exact same stats. I know runoff pH is an iffy stat anyway in many cases, but there it is. 6 is still at the low end of the desired range anyway and the other ones seems fine.

At this point, I can't find any major red flags here other than the possible calcium deficiency. I'm about ready to just chalk this up to having ended up with a picky pheno or something. Hopefully this one will perk up at some point. I'll post another update in a few days.

OK, just want to post a quick follow-up here. In the days after my last post, this plant and a couple others started showing some light calcium and magnesium deficiencies (rust spotting and yellowing between the veins). I've continued supplementing the watering with cal-mag and added some foliar feeding to the mix with a cal-mag spray bottle and all of these issues seem to have subsided. Many of the leaves that were showing the Mg deficiency have started filling back in with a darker green color again. They've also started stretching out again, so growth has sped back up.

So it looks like we're on the mend for now. I'll be keeping a close eye on this, but it does look like I need to keep some regular cal-mag maintenance in my watering/feeding schedule to keep them happy.

I was gonna say after first pics also that it might be cal mag def. Some plants are cal mag hogs, if they are same strain maybe thats a hungry feno

To much to read, check ph of run off and ec/ppm. One or both is off

Quick update. They've all recovered nicely. I also started feeding them once I got past a month or so in the FFOF and they've been responding quite well, but I've been keeping that light (quarter or half doses). Installed a screen a few weeks ago, that's been going fine so far. Other than some slightly yellow tips here and there which are mostly disappearing now, I'm happy with the progress.

rf25532 said:

Quick update. They've all recovered nicely. I also started feeding them once I got past a month or so in the FFOF and they've been responding quite well, but I've been keeping that light (quarter or half doses). Installed a screen a few weeks ago, that's been going fine so far. Other than some slightly yellow tips here and there which are mostly disappearing now, I'm happy with the progress.

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Nice!