I don't think you need a flush, you didn't have nute burn before you left and you didn't feed extra. Don't flush. That's a last resort and I don't think your having PH lockout issues either.... Might need more info on soil and feeds.... as you near the end of the life cycle things start to die off as nutrients needed are pulled out of the fan leaves for the rest of the plant to use because when you start bloom nutes your giving very little N.... Check in at the infirmary for a second opinion but it might just b about harvest time my friend, how are your trichomes looking under a microscope?