I almost clicked on "like", but it isn't an appropriate button. I know Maggy is a cat, but Bo has had "stomach issues" as well, far too often. We seem to have gotten him settled down using "Wellness" dry food, and he loves canned food. Maybe just try a dry food, slowly introduce it over a week or even more, and see what happens. It's really tough when they can't tell you what's wrong, and of course, they'll eat anything we give them for the most part.
I agree with Awsum. If you change Maggie's food, do it gradually. And if the new food you're using doesn't improve things, try another brand. My cat does very well eating Nine Lives kibbles. You could try that, though what works for one cat might not work for another. One interesting piece of advice I read on the Internet is to buy smaller bags. The food is fresher. I think even dry food can spoil in summer heat. The Internet site was discussing the many recalls of pet food, and they suggested a smaller bag because before any ill effects from that batch could take hold, you'd probably be on a different batch, which would be OK. I'm not sure how quickly a pet could get sick from tainted food -- I'd think more quickly than using up even a small bag -- but I decided to get the 5-lb bags, not the 20-lb ones, and I think Tom does better with fresher food. Maybe it's just the placebo effect. I may not really see a difference.

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Things like that bug me.
You'll never find a more supportive bunch Scott.