Need help choosing a cat food!

I have 2 cats (ages 10 and 12). For the longest time I fed them Pro Plan. Then about 1-2 years ago I switched to IAMS. The problem is they throw it up. I mean, immediately after they eat..they step away from the bowl and throw up. Now, I have tried switching from "Weight Control" to "Indoor Formula" to whatever else they have. Nothing is working. My babies keep throwing it up. I'm giving up on IAMS.

My question is..does anyone know of a good brand of cat food? One that is healthy and natural?

Thank you!

BTW - They are indoor cats. One is a little overweight and one is thin. Hope that helps.