Dying Dracaena marginata and Dracaena Fragrans! Please help

I have two indoor trees that I rescued 2 years ago that having been dying every since. Please read the following post for original information and pictures:


http://www.botanicalgarden.ubc.ca/forums/showthread.php?p=220742#post220742

They have gone down hill dramatically since then. I have tried re-potting although I am not sure if I chose a good soil ( what soil should i try and where can I find it ) and we use water out of the tap that has sat for a few weeks to dissipate the chlorine. We water very rarely ... maybe once or twice a month. We have considered a UV light since we get no natural light in our house ( even if it is by a window... which we moved out marginata to and it made it worse). We don't know what type or what wattage we should use... we don't want to hurt them anymore. Any ideas on what light we could try or if we should try a light. We have a horrible green thumb... we love plants and really want them to survive! I would really appreciate any help .I would hate to give up on them after the last two years. I have attached some recent pictures so you can see how they have downgraded since my original post 2 years ago.

 

Try top-dressing your pots with compost and watering twice a week with regular misting. In my experience, dracaenas don't respond well to dry conditions.

 

Roneill, do you see in the last photo the way some of the thinner stalks have bent way over, down lower, but the new growth still looks green at the tips even when bent over? That could also be sign of overwatering.
Kariflips, when you water, do you let the bottom of the pot sit in water for awhile? That's also a big plant, and the new growth has been too small for a very long time; what size pot do you have it in? Which direction is that window exposure?