Ugh...makes you feel sick, doesn't it.......
Have you seen SHB?
Do they have enough honey?
Can they get into and out of the hive freely?
I'm asking the questions because my obs. hive had similar things happening to it this last spring. They ran out of honey, got slow and lethargic, couldn't get up into the tube, then the SHB swooped in and made a mess. For some reason my obs. hive is really slow to take sugar water.
Because of the events, they are super stressed out. I'm not sure why they are dying, whether that be starvation or stress or

. When they die, they often defecate, I think that is most likely the yellow gunk. It would have to be either that or pollen(too thick) or fermented honey which would indicate SHB.
Rick