acidity

This is my first grow and since the beginning they have been growing really slowly. I started them off around 12 weeks ago from a bag of mixed seeds of varying age (all seeds were collected from buds used over a few years). I selected the newish looking ones and germinated quite a few. These are...

Does anyone have any recommendations for sterilized soil used in indoor cultivation? I want to know the highest quality sterilized soil you can think of, and any recommendations on altering the PH of the sterilized soil. I'm also interested in introducing non-synthetically derived helpful...