I have a new kitten and I need advice

So someone left this precious baby in a box in my front yard and we took it home. We think its a baby girl. She was barely 5 days old so we had to feed her milk and eggs with a syringe for almost 2 months. She seems perfectly healthy and has so much strength, she even started to eat solid food and playing. The thing is that she is pretty smaller than the avarege 2 month old cat and I know its normal because she doesn't have a mommy to nurse her and feed her, but I'm still kinda worried because she looks kinda undernourished. But besides that she looks really healthy and happy.

I can't show u a pic because I'm currently writing this on my laptop and the pics are on my phone.

Please if u have any advice or if u think she might have some medical issue let me know.