Thank you for looking out for these little guys.
My guess is that the poorly one has mites - but that is only a guess and even if I am right he needs to see a vet to get rid of them. I believe mites often come out when rabbits are stressed by improper care and illness. I think my vet told me that mites are pretty much always present on bunnies but when a bun is healthy they are able to keep the mites at a normal level. If a rabbit becomes ill the mites can take over.
He could also have the snuffles which is a bunny cold and if I remember correctly it is contageous so try and keep him away from other buns. It would probably be best if you can keep him away from all other animals - just in case but that maybe overly cautious but until you consult the vet it's better to be safe than sorry.
I think the best thing you can do for both of them is to encourage them to eat. I am not sure if you know but bunnies guts should be constantly moving.
They make bunny food. A great one on the market is oxbow brand. Bunny T basics (or something like that) for full grown rabbits is made from timothy hay. They also have an alfalfa based pellet for growing buns. Try and avoid pellets with seeds and colorful things. Buns should have unlimited hay. Hay is probably the best food you can offer them at this time. Timothy hay, orchard grass hay, botanical hay are a few I can think of off the top of my head. Alfalfa is for growing bunnies.
Veggies are also good but should be introduced very slowly to see if they get runny poo from it. House rabbit society has a great site with a list you can feel safe using, www.rabbit.org
Never, ever give iceberg lettuce.
Again thank you so much -you are doing a wonderful thing. Maybe you can explain to the vet what happened and maybe the vet can work you in tomorrow since the buns have already been through so much. The vet will be able to tell you the best way to care for your new babies. Even if the vet can just talk to you tomorrow and answer some of your questions it would be better than my tips.