They seem rather scared and young rats that have been handled from birth should not be like this. Where did you get them from?

I would not give them any food from your fingers, they will associate your fingers with food if you do and wont look to see if there is any when you put your hand in, which will lead to you being bitten.

Have you tried just sitting next to the cage with the door open and waiting for them to come out and explore you? Rats are prey animals and hands closing over them if they are not used to being handled will scare them.

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Jacky and the pet gang