This happen to me a while back. Humidity or sunlight are usually the culprits. in this case i would say it is possibly getting too much sunlight. what kind of exposure does it get? I keep mine in a south facing window, but i also keep it in a terrarium where it receives phenominal amounts of humidity. i would suggest either closing the blinds during the hottest parts of the day, or just move to a different location with less sunlight(east or west). Lipsticks are picky, they dont like too much sun, but not complete shade. Also try to avoid any environmental extremes, which can cause buds to drop. keeping the lipstick rootbound as well, will further encourage flower production. good luck.

Was it cold outside when you transported the plant from the store to your home?

Yes it was! It was pretty cold when I walked it through the parking lot. mpetrizzle, I think you're right about having too much sun; the growing tips look a little sunburnt now. I'll move it farther away from the windows. Thank you!