I have seen this before on some of mine. I though it was calcium, lime scale or something from my hard water over mold. Can you pick or cut it off? Should be fine. Can you see it up the stem?
If it's a fungus, mix a capful of peroxide into a gallon of water then mist the affected area of the rockwool with this mixture. Peroxide is a powerful oxidizer that will kill the fungus.
I just hacked it off...it was on the medium surface. I dabbed the new surface with peroxide on a cotton ball. I posted this in a thread a minute ago but I want to make sure u guys get it. My plant is bleeding after being topped. Its blood red. Is this normal?
