i use advanced nutes stuff at the moment.. i got their kushy kush set that has like 11 bottles of all sorts of different crap, lol.. grow a and b, bloom a and b, momma enbys b1, bud blood, kushy kush, and a bunch of other shit..
i also use cal mag plus and some sweet from botanicare..
what kind of lighting do you use, what size pots, and what's your veg times like?? i've found the longer the veg times, and the bigger the pots, the better the yields will be in the end..
you can also look into some form of training like lst or supercropping or even scrog.. lst is a great method that i'm using now.. it allows you to keep the plants shorter, and get better light penetration.. same with supercropping, although supercropping is a lil harder on the plants then lst, but i still love it and use it in later flowering when the plants start to get too big on me..