It's not always that they're actually a lot bigger, but they are a stockier built rodent than mice for the same weight size which can seem larger from his perspective.
I've not had a BP drop feed for me, so I don't know if it is harder to get those to switch. All of mine strike off tongs for me.
As far as his size goes, they all grow at different rates genetically and some feed better than others or the owner feeds slightly larger prey than another and results in a bigger snake. As long as his body condition looks good, I wouldn't stress a out his weight much.
I generally aim to feed 10% of body weight until they're at their adult prey size (small rat for males, med rat for females), so you could feed about 15g. For me that's usually a weaned or small mouse depending on vendor.
Refusing a few meals isn't be end of the world, though; keep in mind that they wouldn't be eating this frequently and consistently in the wild and that's the frequency they evolved to grow with and handle well.
Sent from my SM-G950U using Tapatalk