I was going to ask if there's a reason you're doing two rat pups instead of just a weaned. Like Dakski said, I would move him up. My BP is about 417ish grams and has a weaned rat every 7 days except when he's in shed.
That being said, I sometimes see him have a bowel movement once every 1-2 weeks. Now this is different than when he was on fuzzy rats, and even different than when he was on pups. As Bogertophis said younger rats are more digestible so when he was smaller I saw a BM maybe every third or fourth feeding.
I don't think you have anything to worry about, but as suggested I'd up his prey size to one appropriately sized item vs multiples.