Right, got an idea for you to mull over.
I tried the Aldi Vitacat brand on our mob when Aldi first moved into my area. Sammy went NUTS for it, would eat a whole bowl and ask for seconds, thirds - then within a couple of days he started to show signs of aggression towards the other cats and my OH, but when he started to overgroom himself, I knew we needed to get him off Vitacat asap.
He's allowed Vitacat stick treats daily, and goodness know what's in 'em but Sam will take your fingers off with them.
I think the Vitacat food must be choc full of grain and additives. All made to be tempting and flavoursome to cats but Sam reacted as if I'd fed him on bad cocaine
He could scale my garden shed in a single bound, and would chase all the girl cats in our street up a tree (oh, he's 13 and neutered by the way!)
Sam's sensitive to high grain foods anyway, he was a bad boy for his previous owners but had never been fed anything but Iams all his life, so they had no idea this was causing his Jekyll and Hyde personality.
Sam's a big softee now, so long as he stays off the
Coke grain.
Defo try a bit of the Purely brand. My lot absolutely wolf the tuna tins but aren't all that fussed about the pouches. The dry kibble in chicken flavour goes down well too. I suggest introducing the new brand gradually as a sudden change from grain to low-grain can cause runny tummies.
BTW, low-grain tends to be pricier, but they eat a lot less as it's nutritionally much higher in protein, so it works out about the same cost.
Get a storage container/tupperware to store the dry food in, it dries out and loses it's meaty scent unless it's kept airtight and they turn their little damp noses up.