I am 15, have been training for about 3 years, and weigh 180. My Bench is at 270, Squat is at 375, and, well, my Deadlift is going to shit. I have a video of me doing a 405 Deadlift, but from that day on, I have not been able to do another 405 rep, and it is actually going down. Two weeks ago I couldn't do 365 lbs., something I could do easily. I stopped Deadlifting and started on Rack Pulls, and tried again today. Same shit. What is going on?
Check your diet, sleep, and all other stuff related to recovery. Take a deload. Try switching up exercise order or something like that.