when u flush ,, pour 5 times the amount of water through your pots,, put em in bath or something to do it, if u can get a microscope at least 30x mag then look at ya trichs and see if they cloudy /amber.
i usually do 1 big flush then give jus water for a week,, its your call on bringing em down,, i wud check trichs first, i think as already said your dead leaves are down to overfert or underfert rather than end of lifecycle,, although she is relatively close.. gd luck