Prepare for a really stupid question - Milk snake appearance

Hi there. I just unpacked three new colubrids, and the two milk snakes (One is a normal, the other is an apricot, both are Pueblan) have black splotches on their bellies. I didn't realize how hard it is to find pictures of pueblan milks bellies. Are these spots just something hatchlings have and they go away, or are they there for life? I find them very cute, so I was just wondering. Also my anery honduran doesn't have them. Thanks.

edit; Also, it is not the 'checkerboard' appearance, they are large round spots on each band on the belly

edit 2; While I'm at it, can anyone weigh in on this? I setup the three newbies in my bedroom that stays around 78-80 degrees during the day, and drops to around 71 at night. With these temps, do I even need to use an UTH? I have them if I do, but I'm wondering if it's even necessary.. my windows don't have blinds so my room gets higher than the rest of the house.

They should have mid-high 80s so I would put an UTH on the tank.

You do NOT need to ad a UTH if those are your average highs and lows. Those temps are fine. The belly pattern will likely stay the same. Good luck with your new snakes!! Post pics!!!