Day 27 today. I got a double air pump and two more air stones that I put right up underneath the roots to provide more air. There is a lot of brown sludgy looking stuff on all the roots under the water. Is that normal?

Some of the leaves on my biggest plant are curling downward at the tips for some reason. There is also some yellowing that seems to be starting. I am going to swap some water out for some fresh stuff tomorrow, at which time I will post some pics.