Dumbbell Rows, huh? Check this out:
Next week, let's try to see where exactly you are at with this. Firstly: you MUST feel this in your upper traps or upper back. That is crucial. If you're feeling it in your lower back or bicep then you're not doing it right. IMO: don't use torso rotation. Keep everything tight and firm. Like a rock.
Try this next week to see how it goes. This system is called Quality Volume.
You start with a weight you can easily do for 3 reps and then you make small increments and try to keep 3 good reps (note: GOOD reps here) and if you can't do 3, drop down to 2 and then finish off with a single. If you want more info, look at my Overhead Press videos from last week. I did: 155x3, 160x3, 165x3, 170x3, 175x2 and 180x1. Same principle.
So, for dumbbell rows:
45x3
50x3
55x3
60x3
65x3
70x2
75x2
80x1
This is what I predict. But this is what you should try to do. Take your normal 3-4 rest between sets and focus on keeping good form.