Post your routine, and your diet bra.........
I don't know about you, but my bodyparts are sore 2 days after I train them rather than the next....therefore, if you did chest and on tris on Monday, you may feel the fatigue when doing delts today..........or you could be burnt out and need a few days off totally.....or, you just might be mentally focused/streesed, etc............tons of reasonably explanations, none of which you want to hear, i'm sure...........doing cardio? What's your goals?
Maybe too much pressing movement and not enough of the support groups, i.e. rear delts,l lat raises, front raisesm uprights.......check out my delt thread......I'll bump it.....