You need a better fertilizer either way. The MG you are using isn't appropriate for any cannabis life stage
I found this ferts 24-8-16 Miracle Grow to be the best thing Ive ever used for the vegatative cycle, it contains all the micro & macro nutes , the high nitrogen content is primarilly urea based (organic form of nitrogen) which makes it almost difficult to burn plants (with the strength I use, 2 LEVEL teaspoons per gallon of water) I feed every other watering and balance the PH of the ferts solution, I expect to see a 1/2 inch a day growth using this

you dont want to use 24-8-16 Miracle Grow if you grow in a confined area