Today after doingmy SS workout I noticed a vague pain in a small spot all the way down in my lower back. I think it's because of deadlifting. I increased the weight to 200lbs today and my back was not nicely arched as normal. However it can also be caused by squatting. I'm not sure how should take the bar out of the rack and take 2 steps back with the relatively heavy weights I use now. When I stand straight up with the bar on my shoulders I feel a lot of pressure through my entire back, not pain, but pressure, I suppose this is normal. I will deload my deadlift and see how I feel afterwards. Is there any way I can find out whether the pain is caused by squatting or deadlifting?

Also, a less important question:
Today I was bench pressing, and due to not very good form on my first set I managed only 4 reps. However the last 2 sets I did manage the 5 reps. I did an extra set of 4 because I didn't manage my 5 reps on thefirst set. Would you consider this as succeeded or failed bench press workout? (should I increase weight or leave it the same next time?)