i have actually adopted a BP and he was left in an apartment for two months with no food/water/etc...since i have adopted (about a year ago) he has grown perfectly but yes i have noticed that my other male BP is still bigger. some factors could be the age of the snakes you are comparing or even the fact that some rescue snake's growth could be stunted if they were not properly cared for in the past. as long as your rescue snake is eating, shedding, etc. and it looks like he has an appropriate weight for his length, i wouldn't worry about it.