Rabbits dropping like flies...HELP!

So, today we lost our 5th and 6th rabbits in the span of a few months, leaving us with only one doe and one buck left. I have no clue what is killing these guys, as they show no symptoms of any kind leading up to death. It keeps happening the same way: We see them all happy, healthy, and exuberant in the morning, and a few hours later, we have dead bunnies. I have no clue what I'm doing wrong, and have never had a mortality rate like this with any of my livestock. We are feeding a mixed forage hay with timothy, a small amount of alfalfa, wild oats, dandelion greens, and plantain. I also give them some sprouted wheat occasionally, as well as small amounts of 'special' type treats, like bits of fresh veggies, etc. They get fresh water twice a day, and have free access to a salt/mineral wheel. They are in a pretty roomy hutch, that is kept clean and dry. Any ideas?

Are they eating sawdust or wood shavings?

I'm trying to think of a disorder that would "one by one" your rabbits over such a long period of time, It's like im looking at an accumulation of something but each rabbit is showing a different genetic tolerance.
Have you done any autopsy on previous rabbits that passed away and found any observational details that you could add? I don't want to shout out mucoid enteritis and have you dwell in multiple fears that have no basis in evidence linked to your rabbits.
But I do want to help even if it's just adding an additional brain to search the internet that might open a door not previously considered. I know what it's like to go from plenty to genetic breeding stock scarcity in a flash, we'll pull together so you don't end up giving up on rabbits.
It's always a bummer knowing when someone gives up there's one less place where life can exist.

check for mold in any hay or grains. rabbits are small animals and takes less exposure to things to kill them.

check whats in your hay. the grass types and weed types. i just had an issue like this and i've come to the conclusion that hemlock is to blame. if you have alot of queene annes lace (wild carrot) it is a look alike with hemlock which is VERY toxic.

The hay I feed is organic and is a specifically cultivated mix of native grasses and forbes for critters like rabbits and goats. I feed the same hay to my goats and they have been thriving on it. We have very few truly toxic plants around here, and none that would be easily mistaken for something else, so I don't think that's the problem, though it's a good thought.

Also, no sawdust or wood shavings in the rabbit habitat. I use only straw for bedding. Also, it is strange that we are losing two at a time, every time, while other rabbits in the same big hutch are fine.

I was worried that maybe they weren't getting enough light. We are in the forest here, with VERY little wintertime sun. Sometimes I feel like I am going to die of sunlight deprivation, myself! After finding the dead bunnies yesterday, I tore the solid wood roof off the rabbit hutch and replaced it with a heavy clear piece of plexiglass, and immediately the light inside the hutch increased 10 fold.

Also, we just had a pretty good cold snap. The rabbits have no heat, but are well insulated in their hutch and have good bedding. What kind of low temperature is the danger range for these guys? They were born and raised outdoors in the mountains here, so I was assuming they needed no special heat sources besides each other to cuddle up with. Maybe they got too cold?

As long as their is no draft rabbits can handle negetive 20 degrees F with no additional heat. If a draft is present the low 50's can be hard on them, when its windy and cold I usually throw in a nesting box since wind gets under my cages. I had a lady who couldnt cull one of my rabbits to eat so she put it in her freezer and two days later opened it up and the rabbit was still alive! I bonked it in the head and told her not to be cruel...lol

possibly ck for any type of mice/rat feces getting into the hay? I had some cattle grade hay kill off a few since it sat on the ground, horse grade is safer for rodent free feed but your orgainic hay should be fine.. ugh

How do you keep yours together, mine will fight if not seperated.

I haven't had any relationship issues with my rabbits. I kept 7 adult females all together and they got along great. Now that I've lost 6 of the 7, and have only one doe and one buck, I have put them together. I am hoping they will breed, but also I didn't want either of them to be alone, as I don't feel good about doing that to any animal. I even did the one thing that is always inadvisable, and put my buck in the doe's cage. I watched for awhile, as I heard that does will always fight intruding bucks, but so far so good. As a matter of fact, I went out to feed these two this morning and found them snuggling in the middle of the hutch, with their faces pressed together, snoozing. I guess I just have zen rabbits.

I was just reading how rabbits, especially young ones or those in packs, are prone to worms.
Maybe an autopsy would help, if white marks are found on the liver this could be an indication.

I agree, first check for worms.
Second, how does their poo look?
They may not be getting enough fiber.
Third, check for mold.