pictures would help dramatically since it could be a number of things, there used to be a post on here about common problems that plants have that might help you. search for it, but it means they are being stressed somehow, either too much water, too little water, over fertilizing, under... there are just too many variables. unless they are being attacked by little critters there is most likely nothing wrong with them and after whatever is stressing them is gone they will perk back up . so if you think you are watering them too often water them less, or wait for them to droop slightly in between watering, that way you know they are wanting some water.