Well first thing is, as I said, don't listen to me - but I'll write some things while we wait. So it may not have been a great idea to flush after the appearance of the nute burn. Flushing can setup a pH problem in soil which will show itself at a later time, something you may have. Because out of range pH can cause lockouts of various nutrients depending on how far and which direction - you need to know your soil pH, possibly runoff as well and those readings need to be taken correctly.
Cold temps could cause the droop and pH is effected by temp as well.
