Babies Eating

[sgocke]

I have four pups, about 3 weeks old.  I read where I should start giving them prepared oatmeal to eat at 3 weeks.  All they want to do is run through it.  Is there something more appetizing that I should give them, or wait and see if they just need time to learn to eat.    I know nothing about genetics and gerbils, but my 2 lighter colored gerbil babies seem to be doing really well, the darker ones that look like their mom seem to be smaller, weaker and not as shaped like their parents (more like little balls).  Is this normal???   Thanks for your help.   Kim and Mitch