Maiden Hair Ferns

You could be overwatering or there may be something eating the roots. Have a look in the rootball to see if anything is unusual nuska1

They seem to be very hard to keep healthy, I have tried several times but no luck I think it is a case of just having the right touch a little like African Violets some people find them hard to grow, some people find them easy.

These ferns are very pretty and dainty. They are not usually hard to maintain. They like moist soil, loose soil so they will drain well. Check and make sure the water is draining from them when you water, if not they will get root rot and stay moist from not being drained rather than from you watering them. They like a cool part sun/part shade area. My experience with all ferns is they shed their leaves every year but they usually come back. You may want to re-pot them in fresh loose, well drained potting soil to give them a new start.