If you see dark or patchy spots on your leaves, that could mean you have mold. Check fordark patchy areas on the leaves and if you do have mold, lower the humidity and get a better ventilation setup going to prevent further occurrences.
And most important.. KEEP YOUR GARDEN CLEAN!!!
Revised: The Complete Guide To Sick Plants,pH and Pest Troubles - PlanetGanja.com

...but I'd fill out the troubleshooting form + pics and post it in the plant problems section to be sure.