Biggesthead

I have grown many outdoors grows in the past but after having my plants ripped off last year I have decided to try indoors. I started off with a 400w HPS, 2 three gallon pots filled with miracle grow potting soil and chicken manure for fertilizer. I planted Jan. 22 and vegged until march 12 when I cut back on the light to a 10/14 on off cycle. By the 21st the bottom leaves started turning yellow and today I noticed the first hairs all around the nodes at the top of the plants. Would this be a good time to apply some type of bloom booster or is the chicken manure rich enough in the necessary nutrients?