I'm going to go off the path here and say that from the pics I don't think it's an overdose of any kind. Usually an overdose will show first in burnt leaf tips and I don't see a single burnt tip in any of the pics.

I had a crop that did this once and it was N deficiency in flower. My pH was all over the place and locking out nutes. It ended up in airy loose buds that were nothing short of schwaggy.

If I'm not mistaken pH is correlated to temperature. Meaning if your res is in the same place (with no heater) and it drops down to the low 60's at night (since air temp hits 50's) the pH will likely fluctuate like crazy. I'm not a hydro grower, but maybe someone else with hydro experience can chime in on this. Just trying to figure out a way that she's not taking up N. N is still needed in flower, just not in as high of doses as veg.

I'm not positive this is your issue, but I really really don't think it's N overdose. Just wanted to throw another idea out there for you.