Quality is a very draining thing for any creator, especially when it comes to his promotion or return to work after a long break. So don't worry about it too much, because at least some chapter is often better than no chapter at all).
As a bad example to learn from. I after one complete rewriting of all my fanfic in pursuit of quality and in an attempt to maintain the pace of writing in the end completely burned out and already as a year can not not write a single chapter without throwing it in the trash ... (Slowly going into recovery in that regard.)
So if it happens, don't give up, get some rest and approach the story with a fresh head, it's much better than trying to squeeze a good story out of yourself and burning out.