They're probably a bit loose because they're not eating bone yet. Eggshells help by adding calcium, but not sure if it affects the poo consistency. I've not heard of eggs helping looseness, but feeding raw egg is fine, so give it a try!

If you're planning to stay at this stage for a while and not move on to organs and bone anytime soon, it's worth getting some of this to try Feline Future Cat Food Company
It's made to be used with just meat and liver, and contains the fiber to prevent runny tummies.
In fact, I have an opened pack that I could send to you to try if you want to - just pm me your address if you're interested

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