eating less with abnormal hair loss... hmm.. if this is a pet rabbit and you have a decent vet AND you don't know what to look for... get her checked out.
if she's not a pet rabbit, but more of a "part of your working herd" animal I'd dust her with diatomaceous earth (NOT pool grade), throw some probiotics into her and see if that helps. I'd also be looking for a fungal infection, thoroughly check her vent, her nose, her front and back legs, checking her dewlap, and giving her coat a good going over to ensure there is not hair loss or mites happening. I would run through ALL other options and treatment methods then before getting her checked out. (one can't bring EVERY animal to the vet if you have a herd).
but if she's your only pet... bring her in. I suspect a fungal infection from what you've said.