A4
From what I can see Stick, I am going to guess N toxicity bro. All those leaves curling over like that and the tips pointing down always puts my spidey senses on too much N. With N toxicity water uptake from the soil is affected which will cause some burning on the leaves. Another thing, you said you were hitting them pretty hard with P. I am assuming what you have been using as P also has K in it? Too much N & K will cause Ca deficiencies to begin showing. Could be why you were looking for pH issues and not finding any.
I always like to give advice as, "what would I do if it were my plants". Generally the last thing I want to do is flush a plant in flower, I absolutely hate it to no end. In this case though, I believe I would flush the entire thing with 1/4 nutrient solution to get a couple of gallons of runoff. Making sure to use very minimum N and bump up the Ca. I would probably be foliar feeding some Ca as well but that is a touchy subject for some growers during flowering but I can tell you from personal experience it works. Ca helps with the transportation of all nutrients in the plant so it will help clear a path to get your plant back on track.
That is just me though. You know what they say about free advice.
I always like to give advice as, "what would I do if it were my plants". Generally the last thing I want to do is flush a plant in flower, I absolutely hate it to no end. In this case though, I believe I would flush the entire thing with 1/4 nutrient solution to get a couple of gallons of runoff. Making sure to use very minimum N and bump up the Ca. I would probably be foliar feeding some Ca as well but that is a touchy subject for some growers during flowering but I can tell you from personal experience it works. Ca helps with the transportation of all nutrients in the plant so it will help clear a path to get your plant back on track.
That is just me though. You know what they say about free advice.
Stickfriend! hello my good brother,...looks like you have a fine puzzle to piece together here,.. I think it's more than one thing going on, but I'm not on a slam-dunk diagnosis just yet,... A4 has definitely put some good pieces down already,...

