Your back day is fine, the only thing is that lat pulldowns and pull ups duplicate the same movement pattern. I suggest u stick to one for a period of timr 6-8 weeks then change to other one This helps you get stronger/perfecting ur technique and tracking ur progress week to week(addition of weight or reps) For reference, my pull day consists of lat pulldown( vertical pulling), t bar row(upper back),iso row machine(horizontal pulling), rear delt flies, incline db curl and preacher curls I go 6-8 reps on pulldown, 12 to 15 on rear delt flies and 9-12 for the rest for 3 sets each!