What Breed Are These Puppies?

A lady I know had 4 puppies that were dropped off on her front porch. She already had dogs of her own so she asked if I could take them off her hands. Unfortunately I was only able to take 2. These puppies are very sweet, but are kind of afraid of people. I think they were abused in their previous home. But anyway, the 2 puppies left behind had black muzzles and looked exactly like these 2. The male is the larger darker one and the female is the smaller lighter one (she was the runt of the litter). I think they might be Pitbull/Lab mix or Bulldog/Lab mix. What do y'all think? I don't really care what breed they are I'm just curious! :) Thank you in advance!