Keep in mind..if you vinegar the skimmer body, it's going to need some time to break in again. I think some soft of bio-film forms on the inside of the skimmer and makes it more consistent.
So are you saying that the skimmer/tank have only been running about 4 days? It often takes skimmers a while to break-in and settle down when they are first started. It's kind of hard to tell since the inside of the skimmer body looks like it's been running a while longer.
This tank has been setup since Tuesday. Skimmer was in my 60gal that was broken down same day. So skimmer has been running for awhile just not in this tank.
The skimmers behavior hasn't changed even though I did about 1hr in a vinegar bath. I'm going to try just the pump and air hose in a bath.