I follow the sample routine and I am on my 2nd cycle of HST. I finished my 1st cycle and did a 10 day SD. I am doing 2 sets of each exercise where I hit my target reps on the 1st set and stop before failure on my 2nd set. My 15 rep max for bench is 135. So my first 2 weeks (15-reps) will be like 110, 115, 120, 125, 130, 135. I did the first week's workout easily, but once I got to my 2nd week, I was only able to do like 8x125 on the 4th workout, but I had done 15x120 easily on the 3rd workout. On the 5th workout, it was still just as bad. What could be the issue here?