Any idea what causes this??

Fox Farm trio is ALWAYS overdone. Their feeding schedule is extreme and is a guide ONLY. It is better to start light on your plants with this nute line to judge what plants will tolerate. I have never ran those high ppm listed. Trio will burn the shit out of your plants and salt up the medium nasty.

Also there is ZERO reason to buy EVERY bottle they list too . Its just a way for you to be separated from your cash. Cannabis doesnt need bottle after bottle of bought shit. Example : SLEDGEHAMMER- flushing agent ..... you wanna know what its really for ?

Its for the growers that overfed their plants on all that Fox Farm stuff you dumped on them. If you have to flush any plant - it is because of grower error in feeding. Which is used to RESET the soil , but with all the water dumped to “ flush “ medium all you are doing is Leaching the beneficial elements - like microbes - ph buffering and elements needed. Flushing does nothing for the plant - it just tries to right the fuck up in excess nutes compiled in medium.

If you are in FFOF ... IMO run water only. Ph to 6.5 BEFORE use. Allow the plant to try to exhaust some of excess on its own. THEN because you are in bloom ( mid bloom ) I believe all of that accumulated nute will power plant enough.

As you get more experience, you will find simpler , more controllable nute lines to use. From 1 part mixes like megacrop / Dr. Earth flower girl / Recipe 420 Ultra bloom or even 2 part feed systems ( grow and bloom ) part A and Part B type nutes. Hell you can even Top Dress more medium soil on top of container and simply water that in .

I started to top dress with more soil and ppl were telling me that’s not gonna cut it.. I’m just gonna go with what you say because that’s what i orig Was doing..so no bloom no cal mag correct ???? How did the plants look to you in the pics i sent?

Top dressing will work fine this far into grow - reason being plant was already acclimated to it so there us no measuring bullshit you have to guess.

It RECHARGES / REFRESHES host medium. FFOF can even be used to make a tea ( on the bag ) and you can do soil drenches with it too.

Top dressing is great also because it is a simplified approach to feed that would highlight any deficient elements if it arises such as a potassium deficiency ( yellow edges / burn mimic ) then you can bump that deficiency instead if trying to figure out what bottle may or may not have been the culprit.

Keep it simple - Remember its just a plant

So was this because of potassium def?

I should add - just because a chart or label says to feed at a certain ppm doesnt mean that plant can tolerate it. Your plant will tell you what it can and cannot handle. All strains are different- some finicky, some hangry bitches.