As we are chatting diet, moreso as they are pet shop, they should be on a high protein diet until around 10-12 weeks old alongside their regular dry mix. It really does make a difference in their development
I get wilko kitten pouches (have 4 flavours and around £2.50 for 12 I think), boiled egg (can also be given in the shell for enrichment!), chicken, oily fish (the sardine tins for 50p good).
If all the diet additions is too scary, I recommend getting Dr,Squiggles to put in their water.
Veggies there is a good safe list list
Vegetables and Fruits
Mine get kale or spring greens almost daily. Kale is like rat catnip! Very good for them too. It can also be frozen to limit wastage. Kittens should have stinkier poop btw so that shouldn't be a aworry, and be aware carrot can make poop orange, I thought it was blood at first!
I make my own mix, I live alone and it is far cheaper, even with a few rats. I and many use Harrisons banana brunch as a base, ,you get 15kg. Then just get no sugar cereals from supermarket, I add wholemeal pasta, rice cakes, rye cakes and dried herbs and flowers as my usual. Also seeds like sunflower and pumkin.. again, atm im ,minus my main base, im managing to keep up my mix via my supermarket orders
Im experimenting with dog kibbles, usually a fish based one best. As already mentioned, shunamite diet is a good guide.. it sounds scary but I really noticed the differene in smell, coats and general condition when I switched from my original.. gulp..science selective.. to museli mixes. It isn't as scary as it sounds, I quite enjoy making up the mixes!
Depending on my group, I bowl or scatter feed. I also do a starve day..where I don't feed them, this helps with wastage but my current mix is obviously a hit as each morning just a few seed husks left
I hope that isnt all too daunting. Putting the work in when young really does pay off with rats