I would add in a rowing exercise on back day and lose one of the pulldowns.
Do leg extensions right after squatting,then deadlifts........finish one bodypart before starting another.
Add in a compound exercise for the triceps.......you are doing two biceps exercises and then pressdowns.............. triceps are 2/3 of the arm,add in some skullcrushers or seated barbell extensions for mass.
Also,vary your rep range by pyramiding up in weight and decreasing reps.......your body will adapt to this set scheme very easily.......besides that,you are only hitting one type of muscle fiber by doing 15 reps on everything.
6-12 reps would be better for upperbody,and 12-20 for legs.
Or you could do higher reps one week,and lower reps the next week.
Good luck!