This week I was repping 275 on deadlift with my main sets. I usually do 4-6 reps per set. On my 4th or 5th rep my grip weakens and I have to put down the bar and redo my grip. So my question is, should I be lowering the weight until I can handle the grip, or does it not matter? I feel like my grip is solid at 245, but going higher it starts to weaken.

Second question. If anyone knows anything about Romanian Deadlift, I started those today. I figured out my form enough to where I was feeling my hamstrings tighten and all that, but I still felt it in my lower back. Is this normal? I'll probably improve my form in time, but I was curious.