One of the things that are important when growing weed is to check the pH level of the soil. This will help to keep the plants healthy by ensuring the soil or water and nutrient solution used in hydroponics has all the essentials the weed plants need.
The weed plants will need to be kept in soil or solution that is between 6.5 and 6.8.
There are pH testing kits that can be found at stores that sell gardening equipment and are easy to use, even for the new weed grower. The important thing is to use one to test the soil.