I manage an observation hive that is kept indoors.

Every year so far we have had to replace our bees (first because they
swarmed and recently because they got sick (dysentery) and the population
dropped).

This is contrary to the "living, working hive" that we are trying to
present.

What can I do for the bees to make them happier/keep them from getting sick?
Would less sunlight help?  Is it the warm temperature they don't like?

Any advise would be most appreciated.

Thanks.