I'm starting weights after about a 6 month break prior to a new AAS cycle. I think this is an ideal time to find what's working, because I get DOMS as feedback.
This week I have done chest, legs and shoulders thus far. My legs are on FIRE - I can barely move them, let alone walk. My chest is the same, Not just a burn, but a deep ache that lets me know I hit it hard. Additionally, my FRONT delts are sore from this workout.

My shoulder routine is as follows:
Arnold press
Machine extensions
Seated front delt. press
Machine rear delt. flies
I do a warm-up set, and then two to three sets to failure in the 8-10 range.

Yet today there is no soreness, no fatigue, NOTHING! My traps are sore, because they're used as an auxiliary, but NOTHING in my mid and rear delts. I feel like I could go right now and work them as if they were fresh. What gives??