If the fixture has good reflectors... yes. But if it has poor reflectors like the coral life t5 NO then its not very adequate light. I have the coral life on my 26 and it is simply not good enough to have truly lush plant growth.
I think you'll find over time that your current lighting is not quite adequate enough to do the job you're looking for, with the plants you're contemplating, although the discus would probably love the low light atmosphere.
I have roughly the same-sized, low tech planted discus tank, with a 36" light fixture of 2 X 39 watt T5 HO bulbs (approx. 3" above the tank top rim) which I feel does a really nice job.
Best way to tell if the fixture will produce enough light would be to borrow, buy, build a PAR meter. This will help you nail the perfect light intensity for a low-tech, which is important for avoiding algea.
If you do need to upgrade, I would highly recommend looking into LED fixtures.
Thanks for the kind words, naturelady and extrame.
As I mentioned, I keep things low-tech simple for discus. I have pool filter sand for substrate, so I use root tab ferts, and occasional moderate liquid fert dosing, and that's it. - 7 hr./day lighting period, and 60% water changes, 2 or 3 X a week.