You will do better with using big bud, carboload, and/or overdrive. Big bud by advanced nutes is what I use and it shouldn't affect you negatively if you use it late, carboload is just a carb so your plant doesnt use it's food reserves and can therefore retain more weight,

and overdrive, (probably your best choice considering your timing) should be used during the last 2-3 weeks before your flushing week, this stuff is sweet it make your bud heavy, fat, and tall. You know when your buds stop growing after a while, well overdrive just forces bud growth down to like 2 or 3 calyxs.

good luck, The nutes above are all advanced nutrients brand.