i bought a small rosemary tree on May 1st. I live in an apartment in chicago, so i keep it in a sunlit window and when i water it, i let it drain out in the sink before returning it to the window. it had such a "full" look when i got it, but since then it's looking more and more unhealthy. many of the leaves have dropped off and the leaves that ARE there are often drooping on nearly bare branches. everything i've read about proper care seems to say a rosemary is so easy to care for. please help... what am i doing wrong?