Welcome to the forum Keez1978...........
What kind of kitty cat is Moo? and we second the motion for pics.
Something I found out over the years is that when cats are having regurg problems, the vet suggested raising the dish because of their anatomy. It's hard to force food uphill and it gets lodged in the throat or esophagus. I started by raising the dishes for our 3 cats about 5 cm or 2 inches and this has worked well for years. Just recently our oldest, who is 13 now, and only 7.5 pounds, started again to throw up. I raised the dish another 2 inches - 4 inches - from the floor and that put an end to the throw up again.
Personally I would stay clear of fish and only use it for a treat once in a while. Remember that cats are a desert animal and they have a tendency to get addicted to the fish which can cause problems.
I go along with Hazel on wet food. I make my own and feed raw to my 3 and it's amazing how much dehydration they go through without being fed wet foods. Case in point, several years ago we were doing a move and for about 3 months I put our cats on kibble. For some reason I wanted to know how much it cost daily for litter, so I dated how long it took to go through a 40 pound bag. It was 69 days. Then I started feeding raw food again once we were settled, and the cats having been fed raw before, just tied into the wet food. And that bag only lasted 52 days. That's 17 days difference.......gives you an idea how dehydrated cats get being fed kibble.
The kibble being labelled "science diet" is only a brand name and doesn't distinguish it as being a higher quality food.
Here is a web site that I think you will find very interesting and informative on what happens to kitties that are not fed properly.
https://catinfo.org/
Please keep us informed of what is going on.......only too happy to help where we can.