There are so many ways to lower the humidity of your 4x4 grows tent with a dehumidifier or without a dehumidifier such as: 1. Don't pour too much water into the plant. The excess water leads to an increase in the water concentration in the air which leads to an increase in the humidity level in your grow tent. 2. Use some fans to regulate the airflow inside the grow tent. Install some exhaust fan that throws the inside humid air outside and intake the fresh air with lower RH. 3. Use a dehumidifier that is one of the best ways to maintain the humidity in your grow tent on per regular basis. 4. Use a proper drainage system to prevent water stagnation. 5. Seal your grow tent properly to ensure that the outside atmosphere can not affect the inside.