What kind of lighting do you have? What are you dosing as far as fertilizers go? Plants' needs follow this order.
Light -> Carbon -> Macro Nutrients -> Micro Nutrients -> Trace Elements
If you don't have sufficient lighting, the plants won't grow. Once you have lighting, if you break the chain at any point before trace elements, you get algae and poor plant growth. Algae is simpler plant matter that is able to do without the whole chain of nutrients. So assuming you have enough light, you are looking into a nutrient deficiency.