Is my puppy constipated?

I have two miniature schnauzers that are 6 weeks old exactly. They have just been weaned, and are currently eating a raw diet (Stella and Chewy's) mixed with thoroughly soaked Evo Red Meat Small Bites. Both are huge, very well developed for their ages, and rambunctious. I had the mom on this diet while pregnant, and have offered it to the puppies since the first day they started eating solid food. One puppy is doing great, no problems at all. The other puppy appears constipated, he's passing his stool but he really has to strain a lot and seems more lethargic. The stool is not hard, it's fairly greenish, while the other non-afflicted puppy's is fudge colored. I'm thinking he may have some sort of infection, but I'm not sure. He's not getting worse and he's still eating, so I'm going to wait until their appointment on Monday for their shots and de-worming. Is there anything I can do to help him feel better? I gave him a little peanut butter and that seemed to help, but I'm worried about the little guy. Could it be worms? His anus is slightly swollen as well.