Can you describe what you’re seeing as ‘bloat’?

It sounds like she is prone to gas, which some bunnies just are. It would be difficult with 3 bunnies living together, but you could try eliminating everything except hay and then slowly reintroducing things to see what her triggers are.

Anything starchy can cause gas, so carrot could be the culprit. Celery isn’t known to cause gas, but it’s also not super nutritious for buns (at least the stalk parts).

I would see if going to a hay and pellet only diet helps things, then slowly reintroduce veg to see what the culprit is. Is Smokey a good hay-eater? Sometimes if they aren’t eating enough hay the other stuff causes more issues.  Some bunnies are also just very sensitive to veggies, but do better with dried veg. Giving a variety of hays can also help give some variety when they don’t do well with veggies.

There is kind of a feed back between stasis and gas. Gas can cause pain which can cause stasis eventually. The gut slowing down can also cause gas. So sometimes it’s hard to tell which came first.

Some veggies are thought to actually help with gas, like fennel. The brassicas (especially cabbage, broccoli, cauliflower, collards, kale) can all cause gas in some buns. Arugula/rocket and bok choy seem to be less gassy in my experience.

FYI the term “bloat” usually refers to true bloat in the stomach, which is super serious, occurs rapidly, and is often deadly. The type of gas you’re seeing is likely in the cecum or other parts of the intestines.

If a bun eats its pellets too fast it’s better to scatter the pellets on the floor than serving them in a bowl. That way the bun has to “forage” for the pellets and can’t gorge on them.

Some rabbits are prone to gas, so it’s wise to do an elimination diet like the others have suggested. Some vegs will probably work better than others, but there is always the odd bun that can’t have any fresh veg at all. My sticky poop-prone bun didn’t tolerate carrot but did very well on fennel, both bulb and herb. Mint is another plant that’s traditionally used for gastric issues in humans, many buns find it very yummy.

I would try one at a time so you can narrow it down. Most lettuces are well tolerated, but if you think the Romain was causing a problem then try the leaf lettuce first.

I wonder if something like endive/escarole might be better? Red leaf and romaine prob aren’t all that different.

Some buns seem to do better with “natural” forage, like dandelion, plantain, mallow, and other safe weeds. Fennel is also supposedly very good for gas, so maybe starting with that would be good? Dandelion is very nutritious in general.