My hair is in good condition, what can help it grow ?*read details*?

I used to have bleached hair a bit longer than my shoulders, Last august i had a reaction to the bleach and It fell out, my hair is now just below my ears and has no colour on it, It is in really good condition, i don't straighten it as i don't need to. The last time i had it cut was probably February, It has grown about 1 cm, what's stopping it grow and how can i encourage it to grow?