1. not eating enough.
2.not taking enough recovery days
3. too much volume.
4. dont know how to get ur lifts up
your prolly getting to the point in your workouts that you cant just go do whatever and get your lifts up...
for deadlifts you can try to start at 135 pull 3 reps add 25-50 pounds and and pull 3 till you cant anymore and pull singles.. do that for two weeks then take a week of deadlifts an do good mornings.. then go back to deadlifts... theres alot of routine you can use to get ur weights up... but deffintely eat more rest more take more off days. but first things first take 5 days off.