If your not doing one more rep, or lifting more weight each workout, then your either
1) overtrained
2) not leaving enough rest days to super-compensate
3) plateaued
4) Your workouts are not effective - perhaps you need to take a 1-2weeks off to de-condition, and when yiu return your body will be soft, reeady to get stimulated again
Usually the first 3 are related
I'm a firm believer in what Charlie Francis says, "what's the point of returning to gym if your not gonna do better than the last time you were there?"
Your deadlifting going down is a sure sign your overtraining - ie working too often without letting your body recover and then super-compensate to be stronger
as a matter of fact, I don't train to failure and only do 2-3 sets per exercise , and yet every workout my reps go up or my weights go up.
Last chest workout I did 3 sets on incline dumbells rows - 1st set I did 7 reps - hard. 2nd set after 2 mins rest 5 reps - near failed. I then used 60% 1RM dumbell and did some explosive 8 reps for power.
Yesterday I used the same weight blew out 8 reps, stopped the set. Next set after 2 mins rest did 8 reps as well, 3rd set did 7 reps and then 4ths set 60% 1RM 8reps explosively for power. Going up to the next heavier set of dumbells next workout and drop my reps back to 6 for 2 sets followed by my power set. When you make progress you feel good!!
This should be a rule, not the exception... but from what I see in my gym, seems like the latter is the case.