If you have a UV filter it wouldn't hurt to run it on the tank. That way if a free floating organism has caused it the UV will zap any of it in the water. Just put it on the outlet side of a canister if you can find an inline one. Or you can even use a powerhead to run an inline one.
I keep an inline UV on hand and put it on any tank that has issues, they are a nice safety net when it comes to weird issues, can't hurt and may help!