Our kittens are 4 weeks old now and we have been trying to start them on canned kitten food. I've tried putting alittle on my finger and rubbing in on thier mouth but they will not eat it. Is it too early to start them on canned kitten food? Everywhere I've read says to start them at 3 1/2 to 4 weeks...All they want to do is nurse off the momma cat. Should I wait until she starts to wean them?