Perhaps it could be related to his diet? Rabbits have much difficulty digesting grains and complex carbohydrates and I see you're feeding BK pumpkin, which is a starchy carb. Perhaps BK has a very sensitive tummy, even for a rabbit, and he is experiencing stomach upsets? Rabbits have extremely fragile digestive systems and if their tummy disagrees with a certian food, it can lead to GI Stasis and can even prove fatal. Rabbits do not have the ability to break down the carbohydrates properly and this can lead to very serious health issues and even death. As a general rule, rabbits should not be fed potato, pumpkin, corn, etc as these are complex starchy carbohydrates.Same goes for nuts, seeds, grain, and legumes.The basic rule is, anything you are considering feeding him, no matter how sure you are that it's ok to feed to him - research it. If in any doubt, don't feed it to him. It's not worth it. One person might say, "oh it's ok, i feed that to my rabbit" but it's far better to be sure and do your own research to have that peace of mind.
Also, when feeding rabbits grasses/dandelions/weeds etc from the garden, it's better to cut a chunk of lawn out and feed it to them this way. When picked, many weeds and grasses release toxins which can be poisonous to rabbits if they are given picked grasses/weeds on a regular basis. Picking grasses from the neighbourhood and sometimes even your own property can be risky because it's impossible to tell if it's been sprayed with weed killer. The people who lived in your house before you may have sprayed the property with weed killer and there could be residue remaining. Even a trace amount in a rabbits system can be fatal, and can sometimes be very hard to detect even by the most rabbit savvy of vets.
During moulting season, rabbits can shed a very impressive amount of fur - you can get handfuls out without doing much more than patting your rabbit. Unless you can see bald patches of skin then it's more than likely just BK shedding his winter coat.
My advice would be to keep him inside, allow him his own space, a place where he can go and rest without being disturbed, stick to feeding him hay and water and pellets (you can add water to the pellets to make them into a mush) and leafy greens (skip the picked grasses/weeds for now, stick to cos or rocket lettuce) and also skip the complex carbs, at least while he is sick. See if that makes any difference. If he isn't drinking very well, insist that yout vet give him a fluid shot. Rabbits can survive without eating much for a few days, but going without water is very dangerous. It's worth a shot!
ray::nurse: :goodluck 
