Did you check to make sure she was eating her hay really well? She should be eating a pile the size of her body, at least twice a day or more, when you aren't feeding her any other foods. Did the small poops start again after you stopped feeding just hay and started feeding other foods, especially any high sugar/carb foods like fruit, grains, or pellets?
Did you check to make sure she is drinking enough water? If she drinks from a bottle, you have to check to make sure it's working and the valve isn't stuck. A rabbit that can't drink, will also stop eating.
Are her fecal poops normally formed or is there anything irregular about them like their shape(not normal round, maybe oval or other odd shape) or consistency(too wet and moist, not dry and friable)?
https://bunssb.org/bunnies/guide-bunny-poops/