Isochain Modified Promethean Mark II - Week 5 Start (needing to back-cycle)

I started today's session with the Shoulder Press, going through the drill-specific warmup. However when I got to the work set, I failed to reach the target load of 35lbs for 2 reps in a row. I dropped the load to 30 lbs and did four more reps of 6-second holds to finish the set. So for the next session, I decided to drop the target load back to 25 lbs. and work my way back up. Sometimes, there's no solid explanation as to why strength fluctuates like this. I felt my general warmup was sufficient to get my shell temperature into training range. This is only the 5th week out of 8 for this routine, so no need to stress. With my elbow still recovering, I really do not want my grip to slip when I attempt a deadlift. I struggled to prevent the bar from starting to slip down my fingers, and thus cause elbow pain, at the target load of 160lbs. So I dropped the load to 145lbs to finish the set. For the remainder of this routine, I will have to treat the Deadlift more as a grip exercise than a leg/core/posterior chain exercise.