... the leaves get black and dtucky?
Hope these sites give you plenty of information! Happy New Year!
You can buy a cheap moisture meter at Walmart for about $10. That will let you know when to water. Are you using fresh potting soil? Do the plants have plenty of drainage in their containers? Are these plants from a nursery? Are the plants getting the right kind and amount of light?
Sounds like a moisture and light problem. Make sure you're not overwatering, and make sure your getting the appropriate amount of light for them :)