I have read that flushing every nute change is a good habit and it has not let me down. If the plant has been burned, like yours, if that's what it is, i use Clear-x in the water. otherwise pure water is fine. the worse the plant the more water up to recommended 2 1/5 times the pot size. let them dry out a little between waterings. I use ebb and grow buckets, fill and drain and always keep my nutes lower than 1100-1200, then taper off on week 7.
pic one 4-6, pic 2 4-14. pic 3 5 weeks into flower and this is the first trim on my worst plant since switching to 12/12. Flush, it can never hurt:thumbsup: