Make sure to clean out the under the trash can.
I have baan having this same issue. tonight I was able to track the severity of the frame rate drops to a spot by the hose reel in the south east corner. in the water under the trashcan there was a pile of apple and hotdog bits that were not only creating a ton of splahing effects but were attracting a large number of black ants and causeing them to act very strange. I jumped in and managed to stop the splashing by wading around in them. it helped but didnt fix it completely.
