Fewer reps could only mean one thing: more weight. Saddle your shoulders with serious iron and get started. In order to reap real gains, you must go heavy.
Show this workout that you're the boss and bring some intensity to the table. Focus on slow, steady, controlled movements that force you to use your muscle and not just maximize on momentum.
I know we're getting to the end of the program, but that doesn't mean you get to forget all about your nutrition. Continue to fuel your body with healthy, whole food that will support your muscle-building goals.