A change to a bunny’s diet is likely to change the size and amount and color of the poop, but if the poop gets smaller, I’d say she’s not eating enough hay. This sometimes happen when you reduce the amount of pellets, the bunny doesn’t fill up on hay as intended but rather just eats less. And that is of course not good.

My suggestion is to increase the pellets again, and then start over and reduce the amount by very, very little, so that the transition gets super-slow. If a bun eats more hay, you’d see bigger poop, lighter (“golden”) in color, the individual poop should crumble if you put your finger on it.

Sometimes you have to try lots of different hays to find one your bunny will like. Some buns prefer stalky hay, others prefer soft hay like 3rd or 4th cut. It doesn’t absolutely have to be timothy, there are other types like orchard and oat hay that some buns like better. (Timothy is good and healthy, but if the bun won’t eat it it doesn’t matter how healthy it is.)