Weird yellowing and brown spots? First grow, help!

Hey guys, I'll start with my problem then get to set up and pics.

So I've been getting some yellow tips recently and I thought it was from too much nutes (I've only fed them 3 times. Currently 6 weeks old.). So I avoided feeding and have just been giving them water. However, the yellow tips are getting worse and now there are some brown spots on my leaves. I'm starting to think I actually have a deficiency, I think sulphur? Maybe magnesium or potassium?

Info-
Temps 70-77 degrees
RH 45-60%. Usually sits around 50 or low 50s.
RO water with 1ml per liter calmag added
3x foot cheese autos (night owl)
6 weeks /42 days today
5g fabric pots
FF happy frog mixed with a generous amount of perilite and some wormcastings/kelp.
Water phed to 6.5
Have never measured run off
Water when pot is light
Feed with FF trio. Last feeding was 1/2 tsp of each of the trio about a week or so ago.
200W true watt LED

Anybody have any ideas? The girls are getting thirsty and I don't know if I should give plain water or nutes to fix this issue.

The yellowing has gotten worse over night

How close are the lights?
FF

FastFreddi said:

How close are the lights?
FF

Click to expand...

About 15-16" away currently. That cola is almost centered under the light so it could be a too much light thing. I didn't know light caused yellowing like this, though.

I can get the light raised a few more inches. After that, the ladies will need to get moved out of my tent to get the lights any taller (which is an option. It'd give them space to stretch out as well. They'd go into a 2x5 closet)

It could be she's getting more N than she needs so she's burning the tips. You can back off on the grow big a tad.
OR.. she's too close to the light, and not getting enough food.

scoob666 said:

About 15-16" away currently. That cola is almost centered under the light so it could be a too much light thing. I didn't know light caused yellowing like this, though.

I can get the light raised a few more inches. After that, the ladies will need to get moved out of my tent to get the lights any taller (which is an option. It'd give them space to stretch out as well. They'd go into a 2x5 closet)

Click to expand...

Try dimming the light to 60-80% if you are going to be that close.

Try the lights, all else seems to be good. Raise and monitor for a few days, if that doesn't resolve the issue, then look to deficiency/ lockout.
Hths,
FF

HydroKid239 said:

It could be she's getting more N than she needs so she's burning the tips. You can back off on the grow big a tad.
OR.. she's too close to the light, and not getting enough food.

Click to expand...

Too much N is a very very strong possibility. I had clawing a few weeks ago and my growth is still pretty dark green. I backed off on it after the first feed of grow big but I think I may need to cut it out completely for a feed.

FastFreddi said:

Try the lights, all else seems to be good. Raise and monitor for a few days, if that doesn't resolve the issue, then look to deficiency/ lockout.
Hths,
FF

Click to expand...

Sounds good! I'll do one more feed of just plain water, and dim my lights. If it's still getting worse by the time they dry out, I'll do a light feed with grow big cut out.

Appreciate the advice guys! The whole grow has gone so smoothly that having something start to go wrong toward the end is super nerve racking. I'd hate to lose my hardwork in the last month of growth.


Pic tax: tents getting FULL

I think I have both a phosphorus and a potassium deficiency. Hopefully the big bloom I put in with their water helps some. Raising the light seems to have slowed the progression. Lights were raised 8" and dimmed. When they dry out I think I'll give them a feed of tiger bloom, unless i've IDed wrong...

Should I give a small amount of grow big as well? Or will the nitrogen in the tiger bloom cover their needs?

Here's updated pics. I defoliated some lower leaves with necrosis that looked like a phosphorus def.

EDIT: Could it be magnesium lock out from ph getting too acidic? Any good ways to check soil ph?