ID for my brown sludge spots.

I have these brown sludge spots that I don't know what they are.
When you touch them it's like a sludge that as you rub it.. it disappears. It dissolves into the water. It grows mostly in the sump but there is some in my display on the rocks. . I'm going to build a light blocker to block the refugium light.
There isn't any type of hair, string, gas bubbles or anything like that. I am at zero nitrate(red sea & API) and .03 PO4.

A while back I had some brown algae that had little clumps that looked similar but it had filamentous hair on the clumps. These clumps don't have any hair. Just spots.