Hi there,
80% of a rabbit’s diet should be grass hay (timothy, orchard grass, oat). (Check out the bunny info feeding section on this site for a full run-down). How many pellets are you feeding?
I think the first step would be to keep the pellet the same (so as not to shock their system), and reduce the amount. For now, you can also pick out the “junk” parts of the pellet to force them to eat the better part.
Super tiny poops can be a warning sign of GI stasis, or some other problem. Not eating as much hay can be a lot of things, from as simple as they are filling up on pellets, early GI stasis, gas pain, dental issues, or just a bad batch of hay. Are you feeding leafy greens at all? What’s their water consumption like?
Try feeding dripping wet greens, fewer pellets, and encourage hay eating by adding fresh hay twice a day. Do you have a rabbit savvy vet you can take them too? If you don’t see improvement quickly I think a vet visit is in order.
I feed Oxbow adult rabbit pellets. You will want to transition them really slowly (esp since they are having issues), and I think the first step would be to pick out the “junk” parts of the harvest food you are currently feeding.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.