Soil run-off dropping drastically each day

I have two plants that are about 3 feet tall and are grown with Fox Farm Ocean Soil in a 3-gallon air pot, and I use the Fox Farm Nutes (Grow Big, Big Bloom and Tigerbloom) and about 1tsp of cal-mag every other watering. I started using full strength recently based on the Fox Farm Feeding schedule for soil and my leaves started getting a little dark green, so I cut only the tigerbloom to half strength. 1/2 strength of fox farm feeding schedule seemed to give my plants some nute problems, such as a bit of yellowing on newer leaves. I use R/O water (~80ppm, 6.6ph) untouched. My plants are in week 4 of flowering and they have nice buds forming on them.

I feed them every other watering. I've noticed the soil PH on the run-off seems pretty consistent, however my PPM changes dramatically from one day to the other. Here is my feeding schedules from the past few days:

When I mix the nutes, I mix it in a 1 gallon jug and I give the plant about half a gallon of the mixture, until I notice a run-off (which usually fills about a half of a solo cup). Each water/feeding is roughly half a gallon. I heard mixed results from people giving their plants cal-mag when using R/O water, so I've experimented giving it some that day and just giving it plain water.

Here are my readings from this past week:

May 2nd:
3tsp Big Bloom
0.5tsp Tigerbloom
1tsp Cal-Mag

Mixture (684PPM, 6.10PH)
Run-off (837PPM, 6.27PH)

May 3rd:
1tsp Cal-Mag

Mixture (316PPM, 6.68PH)
Run-off (608PPM, 6.56PH)

May 4th:
3tsp Big Bloom
0.5tsp Tigerbloom
1tsp Cal-Mag

Mixture (531PPM, 6.24PH)
Run-off (822PPM, 6.39PH)

May 5th:
1tsp Cal-Mag

Mixture (317PPM, 6.72PH)
Run-off (530PPM, 6.62PH)

May 6th:
3tsp Big Bloom
0.5tsp Tigerbloom
1tsp Cal-Mag

Mixture (600PPM, 6.59PH)
Run-off (822PPM, 6.39PH)

May 7th:
R/O water only (82ppm, 6.49ph)
Run-off (230ppm, 6.53ph)

My question is, is this normal for the PPM to drop this much? I've tried looking it up and didn't see any answers on this, but did notice that people say not to feed it every time, and never to give it more than the feeding schedule says.

Here is a pic of one of the plants in question, Sweet Island Skunk (78 days old).

Thanks in advance!

RO water at 80 ppm means it is about time to change your filters. Should be closer to 0. At that point it is a good plan to add back cal/mag at every watering and feeding.

Do you know what the 80ppm is composed of, salt or mineral? If mineral, cut back your cal/mag 50% until you change your filter. If salt, change filters immediately.

The FF feeding schedule is too aggressive for many strains, but your ppms look okay if you were feeding every other watering. I'd recommend going to water only one day and then feed the next day.

Good luck, looks pretty healthy overall!

q42blaster said:

heard mixed results from people giving their plants cal-mag when using R/O water

Click to expand...

I auto feed ca/mg with anything not tap. If not I get defs all day(Hardness 0.7 or less). Plants look Happy to me.

q42blaster said:

is this normal for the PPM to drop this much?

Click to expand...

Assuming: The plants are eating more and like the PH range they are in/@. Looks like they did not like PH 6.2 and under(mix).

Looks like the medium is stable around 6.4 - 6.5

q42blaster said:

that people say not to feed it every time,

Click to expand...

Listen to the plants, they are talking to you. Salts are not your friend is the vibe.

Thanks for the logs, enjoyed thinking abit instead of face palming.

Hey Bugeye, thanks for the reply. I will give it a try. As far as my R/O water, I haven't gotten a good test from the beginning to know how well it filters out the tap water. I live in a desert climate and the tap water is pretty hard and very high, ~900ppm unfiltered. I think all of my filters were last changed about 8 months ago. I will look into replacing it soon.

Cx2H thanks for the reply,

Yea, I've been trying to keep the water that goes in to be neutral (6.5). I've just now started understanding more about how the PH and PPM work, but still have some areas of uncertainty.