Is there light in the room with your res?
I developed brown alage, its horrible and extremely hard to get rid of, common in pools and fish tanks. alot of people think its root rot but its not, its a slim that gets on the roots and then starts to spread to everything in the system. I foolishly thought I had root rot, but the reality was light was shining directly into my tubs, and where I thought the rot started, was actually direct light hitting my root causing alage to grow on the root.
So I tried to treat it thinking it was root rot and it wasnt. my plants are still growing but this shit has me stressed big time. I honestly might switch to a chow mix next run because I cant lose 2 back to back harvests. If I can get similar growth with the chow mix I will eat my words and hire a pro to give JK a blowjob and a box of "im sorry" chocolates
The only cure for this brown alage is physan 20 and UV light. I hit them with 1ml per 10gal saturday and ran it for 2 hours, but Im not sure it took, So I might run it again tonight depending on how the roots look tonight. Physan20 is serious stuff and Im not telling people to use it, because I honestly havent used it before, just going off what some yo-yo's at ICmag suggest. time will tell, Im hopeing thats not what you got