Paul, you are doing a good job encouraging Sukura's kits to nurse. No two ways about it, Momma's milk is best. MUCh better than any formula. Keep an eye on the babies and make sure their bellies look like they got some nourishment after each feeding.
I'm sorry you lost two more. But as others have noted, they could have died from any number of unseen defects or problems. It may not be her fault, and she may not have rejected them. As far as weeing on them, some Does will do that to cover any smell from the deceased babies. It's her way of protecting the other babies.
It is really hard to keep a baby going if it won't suckle. If Sukura is cooperative, try "milking" on of her nipples so there is a drop of milk on the tip. Then put the baby on the nipple. Even a few drops will help.