Frustrating isn't it? My Ali has some tummy issues so I am never really sure we have solved the problem. One issue is she eats too much too fast it's not unusual for dry food to come back up. Since you are just feeding wet food we tried a couple things that worked. Most canned food is too rich for Ali so we went on the Hill's ID for several months too. She never seemed to have issues while on that. When I tried to take her off of that the only food that worked was the Freshpet roasted chicken in a bag in refrigerator at grocery store. I know, grocery store food? yuk right? Well, do a little research
It has very good simple ingredients and it works for her. It's not as messy as canned but it's not as convenient either. You have to use the opened bag in 7 days so I freeze it.
I am still working on finding a dry food. Right now we are trying Fromm but she upchucks that occasionally. ugh
Ali couldn't eat Wellness canned, lots of night vomits. It's great food, just not for Ali.
If you find something that works you can make treats out of canned food. Someone posted how to do it on here. Freshpet comes in soft bite size pieces so that is what Ali gets as a treat. The bite size is large for some little Yorkies but they eat such a small amount, not that hard to cut pieces smaller. Good luck