Green tint on the bottom

[CarlD]

It wasn't at all clear to me that you were using the FAS-DPD test, since you only listed TC.

You either need to get the copper and iron test kit or bring a sample to a pool store and check for metals. If there aren't metals then I'd bet you are fighting algae.

But if you now start fighting algae, you'll need to raise your FC to shock level and it can't drop much, especially overnight.

[ajb8898]

How long do I keep it at shock level since the CC is already 0?

[CarlD]

OK: First test for metals. If you have a metal problem you have to deal with that FIRST.

If there are no metals you want to raise your FC to shock level at the end of the day. Test in the morning and if it has dropped more than 1-2ppm, you need to add enough to raise it back to shock level.
The idea is that when the algae is dead, your FC won't drop. Ultimately, you want it to be able to go 24 hours without a significant drop.