Mystery Illness

I am asking this for a friend.
So I gave my friend one of my kits about 2 weeks ago. He is now almost 10 weeks old. He recently got very ill and I'm not sure what's wrong. Note, I have not actually seen the rabbit, this information is what she has told me. If you have any questions, I can relay them to her.
The kit is housed in an outdoor enclosure with a dirt floor, which is shared by a 1 year old intact doe. He is fed pellets, grass, and vegetables. He was doing very well, settled in with no problems, and got along wonderfully with the doe.
2 days ago, he became lethargic and didn't want to move. He showed no sign of injury, no swollen stomach, no specific pain, was pooping normally. He didn't really want to eat or drink much.
Yesterday, he seemed even worse. No energy, still didn't want to eat. He also had a clear nasal discharge, though not too bad.
Today, he has sat up a bit more, and he started to eat and drink a bit. The nasal discharge has dried up. He is still pooping normally. However, he is now holding his foreleg in an abnormal position. He isn't using it and she says it doesn't seem like he can feel it. I don't know if this is all related or a seperate problem.
The doe he lives with seems fine so far.
She did get new feed a few days before he became ill, but she looked through it and can't see any mold or problems.
She used to own a colony of rabbits and guinea pigs, but they were all wiped out by some type of pneumonia. I don't think it was snuffles because it also killed the guinea pigs, unless it affects them too? We suspected it was spread by the rats they had recently exterminated. Could this be related to the kit's condition?

I don't think it came from me. He had no issues when he was here. I know that herds can carry unseen disease, but I have brought in several rabbits in the past year and haven't really had issues with any of my stock. They've always been very healthy. I have also gotten reports from people who've bought kits from me before and they've all done amazing. And, given the history of bad luck with disease my friend has had on her farm, I think he has picked up whatever he has from her.

Any ideas what it could be? Any advice I can give her? She's very worried. I really am not sure what it could be.

from the info you gave me I'm not too sure, if they exterminated the rats could he have gotten his paw on some poison? also did she desinfect everyting and give it a few weeks to make sure all patogens from her previous infections were gone before getting new animals?

I mentionned poison cause of the limp leg, could be a side effect.
With the little info you gave I think this is a veterinarian visit case, otherwise just wait to see how he pregresses the next few days (if he lives or not)

I'm thinking a short-lived poison, the leg... from how it looks.. broken?

This extermination was almost a year ago, so I don't think he could have gotten to that poison.
However, maybe there was some accidental contamination with insecticides or something on the grass? Maybe he found some chemical.
As I said, the animals are housed in a different environment from the originals, but I still wasn't sure if it is related.
She can't afford vet visits, so I'm not sure what to tell her.

If the leg is broken, is there anything she could do? A splint maybe?
Or would this be a euthanasia case?
I wish I could give more info, but this is all I've gotten from her.