Recovery between sets and cutting

[exter]

I've been losing weight for a while , problem is I've been running into a fairly weird issue.
My best Press was 80KG x2. Last time I easily did 70KG x 4 , rested 3 minutes and failed at 75KG (not a single rep was completed).
My best deadlift was 190KGx1 , today I did 170KGx1 fairly easily(and was persuaded I could do 190) , and then couldn't get 180KG off the floor for a single rep. It sucks.
Any idea why this is happening ?
I'm not on some crazy caloric deficit or anything , currently I am about 18-19% @200lbs

[Jsutt]

I hesitate to point out the obvious, but maybe you had a bad day? Having a crappy day can easily knock 10% off your top lift. You won't be able to hit PR's all the time, every time.

[exter]

It happened twice , on two different days. I'm not sure why the weight is feeling easy and then suddenly I fail after adding 5 or 10KG

[EleikoSwedishSteel]

Have you changed programming? Have you gone down on intensity ?

Finally 3 min rest before doing a heavy single or in your case a test of a max is way to short.