Hi, my rabbits, Maddy and Chris, have been eating a diet of mostly hay these past weeks. Before, they ate a lot of pellets and Chris was over wieght. now they have both lost some weight(I can very clearly feel their back bone). Is this bad?? They are eating well and had parasite control a few weeks ago(REVOUTION kills mites and fleas as well as intestinal parasites). They have beed weighed by the vet twice and they hadn't lost too much weight. How do i know if my rabbits are underweight?????????

Note: my rabbits do not have any pellets in their diet.

If the vet didn't say they were underweight, they're probably fine. Rabbits are actually supposed to be lean but most people are used to overweight rabbits since so many get poor diets/not enough exercise. I think you're just used to the old weights.

What else do they eat? Make sure they get a variety of greens (my rabbit gets all sorts of plants from outside plus some store bought veggies and herbs), too, and it sounds like a fine diet.

What does their diet consist of exactly? While I feed pellets (and I know they're not entirely necessary) a lot of people feed bad food (too much of one veggie) and the rabbit loses weight or gets malnourished.
A small amount of a good quality pellet (martins, oxbow) is fine for adult rabbits and it ensures they receive all the nutrients and basic minerals.