Sad, sad day. My 5x5 had 5 plants in it for my first grow, I'm down to one

my dwc auto. The 4 site rdwc is barren now after chopping a male, then 3 herms. Before the last 3 got axed
Afterwards
At least I'll have one to get to the finish. It's a 7 gal dwc and for the last week it drinks about a gal a day, ppm stays the same, did I lock it out? Also, r these nut burns?
My plan is to drain it, get it to around 600ppm (500 scale,) and add some Epsom salt. Comments and suggestions are always welcomed!!!!