Tea Tree oil is supposed to be an antibiotic/anti fungal/antiviral as well (topical use only--not to be taken internally). Maybe the bees are picking something up from the tea trees, too.
My chickens got into some oyster shale once and their eggs started to smell and taste fishy.
After I eliminated that problem I decided to give them cheddar cheese
cracker treats every day and I must say their eggs were really good.
Someone should do gourmet eggs.