Kiwi is looking underweight. Kitten related?

She's always been a nice sized cat from what I saw of her before she was in my care, and then she was huge from being pregnant.
She had her kittens 2 weeks ago (5 of them) and I've really noticed her weight is dropping. She is very healthy and her appetite is ferocious, she is eating 2-3 cans of wet food a day, and a whole bowl of dry. Not to mention her treats, water, and my bad habit of treating her to peices of my meals. She is eating more than any cat I've ever seen.
I am assuming that she is just fine, and a little bit overwhelmed by feeding all the babies and she will be back to normal soon.
I have kitty bottles and formula here, should I maybe supplement them once or twice a day to give her a break? Should I up her food even more and double her vitamins?
Or, am I just paranoid?

Kiwi should be eating kitten food, and give her as much as she wants, her body needs all that it can get.

The dry food is kitten food.

Matt, give her all the food she wants right now - a good, high-quality canned kitten food is recommended as well as all the high-quality dry she wants. And start thinking about introducing the kittens to canned kitten food this upcoming week - towards the end of the week, closer to the time the babies are approaching 3 weeks old. It is hard work for Kiwi's little body to provide 100% of the required nourishment for 5 growing babies!! All queens lose resources and weight when nursing. It is normal, but can get out of hand quickly if not kept in check. Just feed her all she wants.

Matt, yes indeed. SiSi, who was Sasha's mama, dropped weight pretty quickly after birth and we increased her caloric intake very quickly with wet, heavy and delicious foods.