I agree, I would suggest having them immediately checked for worms and perhaps Ring Worm which is a fungus, not a worm. Could be numerous things but it's not normal for pups of this age to have this. Good Luck.
This sounds like "ring worm" which is not an intestinal parasite but a topical skin fungus which needs treatment. It can be spread to other animals and people. Don't delay this. They need to see the vet.
It COULD be this or it COULD be that. No one can even venture to guess without physically seeing the dogs. Take them to the vet straight away , so that they can get the proper diagnosis and treatment, if needed.
If you are a dog and your owner suggests that you wear a sweater, suggest that he wear a tail.
Well just thought i'd post the results THANKS to everyone who posted some words of advice!! They are fawn black mask boxers & they had some dark hair on their backs they were just shedding this darker hair they are doing fine no mange or worms THANK God!! They now all look light fawn just like their Dad!!! I was soo worried about the babies but everyone is doing great THANKS Again!!!