If you are on a drip system there is a good chance you are over watering. Can we see some pictures please? Also, how old are the plants and at what stage of growth are they at? Flowering, seedling, veg, clone, etc. It is very easy to over water in the beginnings especially if you are trying to run the drip system 24 hours. Ive found a 2 hour off 15 minutes on for a bucket drip system works very well in the beginning stages of growth ie: clone and seedlings. Only you know your watering schedule. You said you usually check every third day but do you water every third day also?

Like these guys said drooping is natural, but only at night time when the plants are "sleeping", then they perk back up in the morning. Just try backing off the waterings a little.