certainly could be.....algea on your rockwool which, amongst other things can affect how much oxygen the roots are getting and that your ph being off could lead to the problem you are seeing.

Off the top of my head....during bloom I'll use 25ml of Cal Mag per 2 and 1/2 to 3 gallons. Are you using RO water? What is the ph of your system at? That's number one.....if you aren't keep tracking of your ph, then that is where you need to start.

I would consider humidity far too high for flowering plants at 60%. I haven't seen fungus or mold issues in plants in real life but it certainly would be something I'd think about here. Or both.....or.....even more.... Anything above about 45% rh will leave your plants more vulnerable to mold.....I aim for the 30% with rh.

Let me find that link.....brb.....
Weedhound Reviewed by Weedhound on . 5 gal DWC Flowering - advice / formula needed I'm flowering two plants, usings 5 gal dwc buckets. Right now all I'm using is: Hesi Bloom - 60 ml cal-mag+ 25 ml liquid karma, 30 ml Hesi super vit 5 drops the ppm turned out pretty high (I was just going by the dosage on the bottle) I think it was around 1700 so I deluted with more water and brought below 1500. I'm using six 42 watt warm CFLs, two 30 watts and they seem to be slightly cooler cfls, and 4 6500k 26w cfls. Rating: 5