The kits should be provided with a nest box with sides high enough to keep them in and low enough for mom to hop in to nurse comfortably. The nest box should have soft hay with a hollowed out part for the kits to nestle into, and that should have been lined with the moms fur to protect them and keep them warm.
If a kit misses nursing with the mom and is looking wrinkly(dehydrated), the kit can be brought to the mom for nursing, though this needs to be done carefully so she doesn't kick out and injure the kit. Usually it involves holding the mom(over a safe surface so neither mom nor kit can get injured) and bringing the kit up under her to nurse. This is best done a while after she has nursed, so it gives time for her milk to have come back in. If nursing from her isn't possible, hand feeding is a possibility, but usually only as a last resort due to the high risk of aspiration pneumonia occurring.
The private area shouldn't look red unless the mom is overgrooming the kit, or if it's getting mushy poop stuck to the bum, which would mean it could have a digestive problem(eg. e. coli).
Teeth marks aren't normal and would mean the mom bit the kit. If the mom is acting aggressive towards the kits and is causing injury, I would keep them separated from her(in their nest box), and only return them to her twice a day in the morning and evening, for just the few minutes it takes for her to nurse them.
https://wabbitwiki.com/wiki/Baby_rabbits_(domestic)