I am seeing the spots on mine also. only on the northernberry but not the skunkberry?? week one of flower after 4 wks veg.

am also using GH 3 part, on hydroton pellets and after adding Mg. thinking it was that, not!

so now I think its a K lockout, due to not carfull mixing of nuits. all three parts need diluted into a volume of plain water before combining them in the right order. if after this last drain and refill(today) this doesn't solve it I am clueless
unless the formula on the bottle just doesnt supply enough K

I will be watching this thread also
Daddy