Are they both still eating?
Could they be eating all their own poop?
You could try let them run around in an area they’ve not been before. They may be a little young for territorial marking but that’s what will make my rabbits poop everywhere. If anything, the exercise will help get the gut moving.
Would trying to induce diarrhea be a last resort thing? There are a lot of vegetables and such in this area, we could go out and get something like that no problem
you definitely don’t want to be seeing diarrhoea. That will dehydrate them fast. Also, introducing greens might be too risky at this time.
Perhaps they’re reacting to the kitten milk. How do their bellies feel? (Right up near the ribs)
Do you have infant simethicone? This won’t help poop exactly but it can help relieve gas pain which might make a rabbit stop wanting to eat. Worth a try…
How much do you estimate they are drinking?