Ditch your routine for tris, and ditch everything you ever been doing for them, it's not working, besides genetics your history with training them has not worked..
Get you rep range around 15.. You should be screaming by the time you reach 15, don't reach 15 with 2-3 more in the tank.
you want to force as much blood and fluids into the muscle bellies as possible. Train for sarcoplasmic hypertrophy, get a decent amount of carbs in pre workout 40-60g, and during workout (intra workout) get down 60-90g of carbs with 5g of creatine (while you are working out/ Carb Gain by NOW is a great product)... Get 5g more creatine in with your post meal or drink.
Use more cables as they keep a continuous steady resistances, more TUT during your 15 rep range.
V-bar push downs - 4 x 15 (lock out each time)
LONG rope tri pull downs, you get a much deeper and better stretch and rage of motion, lock out and slowly back up and hold it so you feel it ripping and stretching your tris and repeat (John Meadows loves these and so do I) 4 x 15
Standing cable skull crushers with short straight bar(face the machine, slightly bend over, its just like doing a skull crusher, make sure you came back to the top of your forehead, and push down and lock out, and repeat) 4 x 15
Seated or standing lower cable behind head tri extensions with v-bar 3 x 15
Weighted seated dips with feet up (plates on lab.. 3 sets until failure, you can use 1 or 2 45lbs plates, have someone take a plate off at failure and bang out a few more, and remove the next plate at failure and bang out a few more.. if you're alone, use 1 plate, and just tilt to the side and let the plate fall and slam them out, and repeat..
Get those muscles heads full, creatine, carbs and high reps (blood) will contribute to sacrcoplasmic fluids..