Normal ? Yes and no.
It is expected when your brake calipers, especially the pistons are dirty.
When these pistons get too dirty from brake dust and maybe a little bit of oxydation, they won't be able to come back to their neutral place as freely.
Right now it is not too concerning but you should at least spray a good amount of brake cleaner on the pistons to try and free them a bit.
If you feel you're able to try, try to unbolt your calipers and clean them with brake cleaner and a toothbrush (used one, don't go brush your teeth with brake dust! )
Even better ? Get a brake rebuild kit for both rear calipers and install them. But that takes some know how I'm not sure you have right now.
In any case, that is not dangerous right now after a good spray of brake cleaner.
It would be a good occasion to make sure your brake pads are in good shape at the same time !