Sounds like overwatering. You are supposed to give it a good watering so that it drains out of the bottom of the pot well. Then it should take several days to dry up. MJ thrives with a bit of a drought period INBETWEEN waterings. If you have watered well and have proper drainage you should be able to wait a few days with NO watering. You are not supposed to water again until the pot is light as a feather. I usually water every 4 days or so. The rate that the plant uses water is dependent on lights used and the heat of your environment. For instance my temps are low 70's and I use LED, so it can take 3-4 days for a nice size plant to be ready for water again. If I was using an HPS light it would dry out my soil quicker. Most common mistake is over watering. I kid you not, MJ likes a bit of a dry spell.