The Burgess hamster mouse and gerbil isn't the best diet and only has 15% protein. So yes switching to Harry Hamster would be much better. You can get it online
This is for two packs
https://www.amazon.co.uk/Pack-Suprem...8891697&sr=8-4
I don't know what Nature's touch is. A good basic muesli with the protein levels daily should help.
When you do switch foods though you need to do it gradually over a couple of weeks so their digestive system adapts without upset. So maybe add a bit of the new food for the first couple of nights, then a bit more for a couple of nights, then about 1/3 2/3 mix for 2 or 3 nights, then 50/50 for a couple of nights, then 75/25 for a couple of nights then switch.