Is this a 3rd rabbit or one of the two that you were keeping separate until fixed?
Photos show early signs of GI stress. How old is he and how long have you had him?
If he is new to you, then he should have remained on the same pellets he was being fed at the pet store. Then you can slowly transition him to your preferred pellets by mixing the old with the new over a period of a couple weeks. If he's already eating the new pellets, leave it be. What kind are they and how much is he eating per day?
No new greens for several weeks after he's brought home -- it's too easy to upset their bacterial gut balance. When it does come time to offer greens, only one type should be offered. That one type will be tested. Small amounts offered at first, looking for any change in poos. Gradually offering more of that same type over a period of days if there is no negative reaction or change in poos. Details for how to safely and properly introduce greens can be found at the link below.
No treats whatsoever. Those can wait til months down the road.
Try refreshing the hay throughout the day. If he's refusing and he may sit scrunched in a football position, then you can offer some simethicone (baby gas drops) for pain. That often is enough to get them eating again. Eating gets that gut moving and back to health.
https://rabbitsindoors.weebly.com/greens--veggies.html
