I have a dracaena that I got in college I think and it's had yellowed leaf tips for as long as I can remember. I decided to do a little searching online recently and found out that many houseplants and dracaena in particular really don't like the chlorine and flourine in tap water.  Here's the link I found:

http://hgic.clemson.edu/factsheets/HGIC1504.htm 

So good to know! Try using bottled water or collect rainwater for your plants.

Will Cray