Although, I am not able to address your question as to what has happened to your pearls in the last month......I can tell you that depending on where you purchased your pearls (trade show, show room) the lighting is set up to deliberately distort the true appearance of pearls (and gem stones) and will always make the pearls appear much better than they really are. Luster always appears better and colors look darker. Also, blemishes may not appear as severe under those lights. Unfortunately, this kind of deception is legal.
Gail