Right offhand I would say fungus or bacteria. And while there may have been a change of conditions from the store to your house, the store's in your neighborhood, right? Do they keep it *that* air-conditioned?
I don't think it had anything to do with anything *you* did. You haven't owned it long enough. Had the plant stayed at the store, I'll bet the same thing would have happened over there.
Use a single edged razor blade or a clean (wiped down with alcohol) pair of scissors, and nip off the bad flowers and the buds that blasted. The others may still be ok. Also, spray the entire plant with a fungicide / disease control like Orthenex.
(Maybe those stores do that kind of thing on purpose: sell diseased plants so they can then sell the stuff that fixes it.... Ok, they probably don't do that, but still, other than Traci's tolumina, every plant that's had problems on this board has come from one of those stores. Makes ya kind of wonder....