Can't make up her mind

Our new cat, Dolly (the cat formally known as Luna) has had some bowel problems since we first got her home. Recently, we finally got her straightened out with Performatrin Ultra and she's been regular and consisitant. Suddenly after a month of loving the dry food, she stopped eating. We got her Natural Balance Venisen and Green pea and she (and the other cats) all adored it, gobbling it. Now that it's been another month, she's stopped eating the dry again. Should we just go with this flow and change her food once a month? So far no more bowel problems, but it just doesn't seem normal.
Maybe she's just not normal. No, scratch that. She definately isn't normal regardless of her food issues.
Any thoughts?
Jess

Many cats get loose stools when food is switched, and people have to switch gradually over two or three weeks to avoid that. I'd say that if you're NOT having a problem like that, go ahead and switch the food periodically. Some cats just like variety. My Mellie won't eat the same canned food more than two days in a row.