Over watering will cause root rot. The plants can not then take up water and they will wilt. If you under-water the plants they will also wilt. This can look similar and can be a little confusing. Better to under water slightly. If I forget to water I sometimes see that the leaves are a little limp and then water and they perk right up. Error with a little under watering. I have read many many times that over watering is the most common cause of failure in growing a plant.
