Green tint on the bottom

[ajb8898]

Hi, I've been having much success with the BBB method this summer but in the last two weeks I backed off how high I was keeping my levels. The pool developed this greenish coat on part of the bottom of the pool. I stir it up and it quickly floats away. I don't see any pieces of algae. It almost just seems like dirt but my sock is turning green. I've been maintaining my chlorine level back up to the regular level (10) and brushing/vacuuming several times a week but it's still not going away. The interesting thing is my kit is not registering anything growing.

CYA: 40-45
TC: 7
pH: 7.2
TA: 130

What is it? Do I need to maintain shock level to get rid of it?