I would recommend keeping them in different cages and allowing them to play together. Bunnies may get a little lonely, but it is better than having them fight, even if it is not major fighting. Bunnies will usually have some territorial issues unless they have been together since birth or a very...
I use Organic Unfiltered Apple Cider Vinegar for mine and have found it very helpful. I have 64 oz water bottles and I put a tablespoon in each, once a week.
I hope this helps! I love the improvements I have seen in my herd of Hollands since I started using it weekly!
OMGoodness! They are all the cutest pictures, you have some lovely bunnies there!
I saw a little block of something that the American Chinchilla looks like she is sniffing in the first picture, is it a snack? Mind sharing? I am really wanting to find some good snacks for my bunnies, but haven't...
I would sincerely recommend getting a new buck, if the doe is very receptive it would be wise to get a new buck while she is still in the mood. Even if the buck can breed, he may bring some unwanted genes into your rabbitry.
I would recommend keeping an older one and then the younger one. The older one to continue to get outstanding bloodlines form, and the younger one to begin to take the older ones place and eventually become the main herd buck.
Hope this helps, best of luck!
Just something to keep in mind, as soon as you breed a young doe for the first time she stops growing. Of course she can gain more weight and all, but she stops her overall growth right there.