Why does rosemary appears to be drying out at the tips?

I've recently bought two small rosemary plants (can't say they're bushes yet). They're beautiful and dark green, but from a closer more detailed view they appear to be drying out at the tips of their twigs. I keep them in my room - which has a huge window that I keep open at all times, and is relatively shady. I take them out for sun 4 to 8 hours a day. I give each of them a test tube of water a day. Also, I'm planning on using grinded lemon peels to revitalize the soil. I'm really worried. Please help? The one plant got it's first flower (on my watch) yesterday, and I'm really scared what ever the problem may be will affect it... Please please please help?