Earlier today, when I was checking the litterbox for Ms. Rabbit’s poop (which is big and healthy, by the way!), I noticed that there was a lot of dark-colored poop in the litterbox. Upon further inspection, they were a mix of giant cecals and very mushy regular poops. I wasn’t sure whose they were at first, but I’m pretty sure they’re Mr. Bunny’s, since they’re way too big to be from Ms. Rabbit. I’ve waited a few hours to see if Mr. Bunny made any more, and there were about 10 brand-new, even more mushy poops there when I checked back. 
Mr. Bunny seems a little bloated and has a few hard spots on his belly, but he’s eating normally and seems to be in a good mood, although he’s a bit lethargic. I noticed that he was reaching down every 30 seconds or so to get a cecal when I was petting him earlier today.
I haven’t changed their diet at all for a couple of weeks. The only new things they’ve gotten were a few pieces of watermelon two days ago and a few crumbs that he ate off the floor yesterday. Is this something that I should be concerned about?