Over the past year i've had the same problem on a few of my lifts, they'll get really strong (one at a time), and then they'll just shit the bed and i cant figure out why.
e.g last summer my deadlift added a serious amount of weight in the span of three months. i went from 325x10 to 415x7. about a month later i was at 405x2. Same thing happened with my squat and military press this past month. I take a deload every 4rth week.
thanks in advance