rabbit grows, poop doesn't?

Oh dear, I feel like I pose a lot of questions. Thanks for bearing with me, forum.

So I have two minilop mix bunnies, siblings from the same litter. They're nearly 3 months old now, and here is how big they've grown:



Rose (white) is a little bigger than Merlin (grey), always has been 'cause Merlin was the runt of his litter. But look at their poos, fresh from today:



The smaller ones came from Merlin, the big ones from Rose. I swear, Merlin's poos haven't changed in size since the day we got him and he could fit in my hand. Now he's doubled in size and his poos are still tiny. Rose's poos have gotten gradually bigger as one might expect, but they've also gotten somewhat softer and smellier.

Is she the one with the problem? Is he? Is this normal or vet-worthy?

PS. I should note that the "smelly"ness was a recent development. We just got them a bag of ryegrass hay when we usually get meadow, not sure if the hay change is the cause? We're going back to meadow as soon we can get some, it seems like they don't like eating the new hay.

Her poop might be more smelly if she is starting to get her hormones in. They have scent glands between the genitals and anus, and it can be pretty smelly when they start marking their territory. It has a light skunky smell to it.

The differences in their poop size will have to do with what they are eating. Does she seem to eat more hay than him? Her poops look really good. His are a bit small. What do you feed them each day? Does he tend to eat more pellets then her? I would say that he needs to be eating more hay and less pellets, and that will help get his poops looking better.

Just fyi, if you are still keeping them in the same cage, at 3 mo. old they can become sexually mature, so it would be a good time to separate them into their own cages, but I would put them right next to each other, to minimize the upset from the separation. You can still let them play together if you want, but you need to very closely supervise, to ensure there is no humping going on. Once that starts it's best to end their playtime together until they are both fixed.

She eats more, definitely. Of everything. He doesn't seem to have much of an appetite for pellets OR hay despite my best efforts to feed him up so he'll "catch up" to her in size. He's much more interested in running around and being crazy. She's more mellow and sits around either eating or searching for food. I don't really know how I might encourage him to eat more hay!

They're booked in for a vet visit in two weeks for a well check and to see when they can be neutered. We're gonna do it as soon as the vet is willing, so hopefully there won't be any surprises in the hay.

Also, Rose's poo smell has gone away! They've gone back to being hard-ish and not smelly. Must've been a brief bunny bug or something?

Size is a hard thing to figure. Our 20 lb Checkered Giants are five time as big as our 4 lb mini, but I had a male Hotot that passed the biggest ones we've ever seen and he was a fouth of Serenas' size. It does relate to how much hay they process and Stew was a little hay eating machine. Finn eats as much hay as our big girl, and while his don't match up in size he is much more prolific. The only smelly ones they've left have usually been cecals or when they are a tad "loose".