Bottle kittens

I have some bottle kittens that were dumped on a local road. I’ve had them for almost a week. I had trouble getting them to poop at first. I’m sure the KMR contributed to that. Everyone finally pooped yesterday. Now they’re eating way less than they have been. The vet estimated them at 3 weeks old. Each kitten weighs about 28 grams and was eating 9-13 cc’s a feed at first but now 2 of the 3 are only eating 5-8 cc’s a feed and the runt is eating around 10.

Could this be because of their pooping trouble? They all had to work very hard to get the poops moving. They slept a long time after they finally pooped.

Should I be worried that they’ve slowed their eating down? I will call the vet tomorrow.