Seedleranswered grow question a day ago made me chuckle, no, its probably not Botrytis hahaha
Thats like google your symptoms and then thinking you have cancer when you just got a cold.
Did you check your root zone pH? like ever measured the run off water? it bet the pH is fucked and thats why other nutrients can't be up taken anymore
Thats my guess, get the pH from the run off, water with pH water to correct the root zone, good luck!