Sounds like your snakes are either at the 2 pinkies stage or the 1 fuzzy stage and that what you call a fluff is what we call a fuzzy. A lump 3-4 days after feeding suggests to this noobie that maybe it's kind of a big meal for your snakes, but if they are growing, pooping and NOT REGURGING, I probably wouldn't change anything. Now, if more experienced folks have a different opinion than mine, go with THEIRS as I am new to snakes.