Kitten maturity levels

I have 4 kittens, 6 weeks old, all from the same litter; 3 female and one male. I've been trying to get them weaned since they were three weeks but they had no interest. The male was the first to sniff and eventually eat the veal baby food we offered them, and soon, one of the females followed suit. A few days ago I offered all of them some dry kitten food, and the two who were beginning to eat solid food enjoyed the dry stuff immensely. Then one of the other two slowly crept over and began to eat, as well. The very last one (the runt, I should mention) is still disgusted by anything but Mama cat's milk.

My question is, do kittens have varying maturity levels? Should I concentrate on getting the last one weaned, or should I let her take her own time? Also, all four still nurse frequently; should I try to limit this while I'm trying to get them weaned?

Kittens usually develop in order they were born. I know its a little weird, but they do. At 10 weeks if the little one is still not eating solid food, I would try to encourage it. Don't worry about the weaning, mom will let them know when it's time. She will not let them eat when it's time to eat on their own.