Maybe the horse is already out of the barn on the quarantine end if they've been together for two weeks already.
It sounds like you're doing a good job so far, and keep the inches between them if Kasey is off his feed. When I let my rabbits loose in my yard (ONE rabbit at a time!!!) they go and check out each other's cages and eventually begin to hang out by the cages, doing their rabbit thing. So you could try that initially when everyone is feeling better. Let one out at a time, that way the other rabbit has the safety of a cage between them if the other decides to go bonkers. Rabbits wanting to fight through a cage looks VERY different than rabbits greeting each other through a cage. With greetings and happiness there is lots of bouncing around and nose nudges and eventually the other rabbit may lay against the cage in a buddy-buddy fashion. Fighting through a cage usually involves violent movements, boxing, attacking the cage, trying to get to the other rabbit in an aggressive manner.
This is just my experience.