Breeding maybe being weird??

Hi all, I don’t know if this is a glitch or just a normal thing that I’m looking at too hard, but I breed my wolves and have puppies pretty frequently, but the last maybe... 5 or so times all of the litters have only had 3 puppies (and also usually two of them have only 2-3 markings, while the 3rd has many markings, but I think that’s probably just luck). Is this a bug or am I just getting unlucky lol?

It’s probably just back luck, I’ve had times like that too lol