First I would stop all foliar spraying.
Second I would handle my Ph “issue”.

Ph down is full of sodium. Acting in the same manner as baking soda being a great alternative to Ph down products. But it is detrimental if used regularly as it dehydrates the roots and plant performance.

The Ph shouldn’t need intervention unless close to the end of a swap cycle to keep the water in Ph range for another day (because you had healthy Ph creeping up) until you can swap.

If Ph is between 5.5-6.5 no Ph up or down should be used. Only force Ph if it is completely necessary, but it should never be if you have proper PPM and water temps. Also, never drastically reduce Ph, example: 6.2-5.4 .8 Ph flux is going to shock the plant. Plus increase sodium, two fold stress.

A chiller shouldn’t be needed if you insulate your bucket properly and take the extra time to wrap your bucket. If water temps are 65-70 you are fine. Also. Put the bucket on a surface that has a temperature near or at your target water temperature. As the bucket temps with try to match that of the surface it is sitting on from temperature transfer. Find a colder surface to put the bucket on.

The desired Ph should be 5.8-6.5 in flower and is acceptable to let it go if in those ranges.

If you have Ph swinging (aggressive/spike) intraday or even over a 2 day stint, you need to lower PPM. (And it isn’t due to water temps)

Water temperature swings will also adjust Ph. By roughly .1 Ph per 1-2 degree water temp change. Water Temps go up, Ph goes up. Water Temps go down Ph goes down.

Plant uses nitrogen in veg stage a lot, as she uses it she drops Ph.
Plant uses phosphorus in flower stage a lot, as she uses it she increases Ph.
Which these changes should be minuscule and is how the plant controls her food availability and maintains Ph by herself. Hence a slow creep in Ph is acceptable and still healthy, only swings are considered a signal to make a change. (Lower PPM and swap).

Whenever your Ph swings and it is not due to water temp changes, the correction is to lower PPM and swap the reservoir. This is by default the corrective action for unstable Ph.

If PPM rises in the reservoir, it is corrected with reducing PPM and swapping. That is first sign of nutrient lockout and the plant ignoring nutrients and drinking water only, in turn increasing the PPM.

These are basic rules of hydro.

Hydro also requires a lot less PPM to grow great buds. So keep your feeding on the light side all through the grow, trust me, it will increase plant health, stabilize Ph allowing the plant to do its thing with it, and most of all increase success rates.

If your fungicide spray has copper in it, you disrupt nutrient cycles of the plant. If prolonged use and regular use of it, you can cause copper toxicity. Copper is used to create Lignin. Pho synthesis is hindered with a copper toxicity and will cause fat stubby leaf growth with yellowing followed by browning.

I don't grow with hydro and I probably can't help with your current issue but I found this chart awhile ago, it may be useful to you

If that fungicide is used in the water, I would swap and never use it again. It shouldn’t be needed at all especially in the water. No fungus nutrient that claims to be beneficial will help your hydro plant. It will only create problems. You cannot achieve mycorrhizae in hydro and it shouldn’t be attempted with claimed products to do such, in the form of liquid fungi. Products can mimic it like GH Diamond Nectar, but in no way should you add a fungal liquid to the reservoir. I have only seen a couple products claiming to have beneficial fungus for hydro, but it’s marketing and shouldn’t ever be used.

That is my personal opinion on those products.

Hydros weakest link is mycorrhizae and it cannot ever be present in soilless mediums without detrimental damage. The only thing that puts hydro down vs soil.

Newty said:

I don't grow with hydro and I probably can't help with your current issue but I found this chart awhile ago, it may be useful to you

View attachment 2181143

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As brutal as that chart is, with corrections being to swap and lower PPM. It is true. Basically what this chart will tell you against your readings/findings of your hydro plant, is that you probably are overfeeding if you have any of the issues.

“Hydro also requires a lot less PPM to grow great buds. So keep your feeding on the light side all through the grow, trust me, it will increase plant health, stabilize Ph allowing the plant to do its thing with it, and most of all increase success rates.”

This is the biggest takeaway from my nasty long post. For a beginner, it is the only advise you really need. No products to control anything are needed. Not even water temps…and I’ll be honest, I have no idea how fungicides will keep water temps in check and have never heard of it or looked into it. I always just wrapped my buckets with reflectix and water temps don’t go over 71, even in 80 degree room temps. Possibly in a tent you may find the water temps rising a lot but for a room with Airflow, you shouldn’t have water temp issues if you insulate the container/bucket. Then again, it could be that I put my containers on a bare concrete floor.

Also if you have Ph swings increasing PPM is a no no.

Bdubs said:

If your fungicide spray has copper in it, you disrupt nutrient cycles of the plant. If prolonged use and regular use of it, you can cause copper toxicity. Copper is used to create Lignin. Pho synthesis is hindered with a copper toxicity and will cause fat stubby leaf growth with yellowing followed by browning.

Click to expand...

That sound like what’s happening new growth is almost single fat leaves that turn yellow then get the rust and go brown and dry crispy