I started lifting seriously in January, and followed a good diet. This is the routine I was following during that time:

Monday - Chest, Triceps
2 sets incline dumbbell press
2 sets flat bench dumbbell press
2 sets lever chest press
2 sets lever bench press

2 sets dumbbell kickback
2 sets lever triceps extension
2 sets cable pushdown
2 sets skull crushers

Tuesday - Legs
2 sets lever leg extension
2 sets smith squat
2 sets seated leg press
2 sets dumbbell lunge
2 sets lever lying leg curl

Wednesday - Back, Biceps
2 sets cable seated high row
2 sets compound rows
2 sets cable straight back seated row
2 sets dumbbell lying row
3 sets wide grip pull-ups

2 sets dumbbell hammer curl
2 sets dumbbell seated concentration curl
2 sets lever preacher curl
2 sets barbell preacher curl
2 sets barbell reverse grip seated curl

Thursday - Abs
3 sets seated lever crunches
3 sets decline bench crunches
3 sets weighted dumbbell side bend

Friday - Shoulders
2 sets lever shoulder press
2 sets lever lateral raise
2 sets front dumbbell raise
2 sets dumbbell shoulder press
2 sets cable upright row

I did mostly 2 heavy sets of 4 to 6 reps, but not max-ot. Should I change my routine around a bit and continue what I am doing or jump into max-ot? My gains started to level off a bit, so I am looking for some help.