Adding fresh yeast to 'clean up' flavor flaws?

I recently brewed an extract-based Belgian Wit. 3 weeks in the primary with While Labs WLP400 Belgian Wit Ale Yeast, and then 2 weeks in the keg in 'set it and forget' mode.

Upon tasting, the initial flavors are very good - what one would expect for this style of beer. But soon, an almost 'plastic-like' taste develops on the side of the mouth, not the tongue. Sampling form the keg vs. the beer lines yields the same taste, so it is not the beer line. It is a pretty noticeable taste and I am almost afraid to share this particular batch with others.

I am thinking I fermented too warm (carboy was in a closed bathroom with it's own heating vent, so the room can get quite warm if the door is closed) OR perhaps went a little overboard in "rinsing" the grain in my grain bag during the brew.

Anyways, I was wondering if, as some people to do remove diacetyl after-the fact, if adding a little bit of dry yeast and priming sugar to the keg, warming it up, and letting the yeast do their thing might allow the yeast to perhaps metabolize whatever compound is responsible for the flawed taste?

dont add more yeast. just control your brewing process next time. add enough yeast and control your fermentation temperature. both of these will help keep the esters away.

or just wait longer. there will be a point where the yeast aren't going to clean up any more and your just going to have to live with the result.

Definitely worth trying, but plastic/solvent-like flavors probably won't go away. Since you've kegged and carbonated, definitely re-hydrate your yeast and be prepared for a foam explosion.