flowering

hi...i have a 7week old chocolate chunck plant 3days into flowering and it is 3feet tall, it is in a 2gallon pot, dont remember what kind of soil, it has bat guano and some other things in it like that, from what i remember. iv'e been using 2-1-6 flor-a-grow for food during veg, and i just recently bought some bone meal, but somebody told me it has to be mixed into the soil from the start, or can i still use it by mixing it into the top layer of soil, im just trying to figure out what to use for food during my 55day flowering period can anybody help......could use some advise.