Yellowing setiva 19 weeks into

Been growing a long time I have one plant, its the best one, that has a little bit of yellowing Ive added bone meal about 2-3 weeks ago seemed to help a bit.
My question is should I add a bit more to completely rid of yellowing they are about to flower and I dont want to burn them, I dont know much about bone meal will it burn?
I did 2-3 tbl spns per plant in 15 gallon containers.