HELP!!!

My bunnies recently passed away. They both began with the same symptoms of blood in urine ( about 3 months) and then one day having diarrhea before eventually seizing and passing away. Both symptoms showed 2 days apart from their death. I immediately rushed each one to a hospital as soon as i noticed, but eventually they passed since I wasn’t able to afford the aggressive hospitalization they suggested. I was offered a free necropsy for both, but my male died at home while my female died at the hospital on different days, so we buried one and allowed the necropsy done on the female. I recently got my results being told that their GI tract was basically just black when she opened it up and that could have been the cause of death but she couldn’t say with certainty due to not being to run any diagnostics on them when they were still alive. does anyone know what it could have been? I just want it for peace of mind and if i were able to ever own a bunny again to stop it from repeating. I included images of their state when first noticed, one being worse than the other assuming the female was having diarrhea all night while the male was immediately rushed as soon as he started.

by yngycky