Inactive merit sources should be replaced with a new one, IMO.
I don't know what is the process of sending smerit per merit sources but it seems sending 20+ smerit in one post isn't looking good, it might reasonable if that 4-5 smerit in one post, my question is, are they tired of distributing on it?
Number of merits for a post is subjective and it depends on the merit sources and their monthly allocations, but all they claim is they don't find enough quality posts to merit them, so time can be the major factor not their are tired I guess.