I know this thread is a little over a week old so you're probably already done, but I'll chime in for if anyone else finds it later on.
For me, I don't have a set way of doing a deload week. I just go by how I feel. If I feel totally run down like OP said, I'll take the entire week off and rest.
You would still want to incorporate some form of activity like walking or playing a sport or something so you're not just sitting around on the couch, but I don't do anything too strenuous.
Other times I'll still hit the gym but cut everything way back (sets, reps, intensity). I essentially do what would be a typical warmup and don't go any further.
Sometimes I'll work up to a few "heavier" singles just to keep my strength there, but these are nowhere near my 1rm. Maybe 80% or so.
The important part is not to really think too hard about the deload week. After all, it's a break for your mind as well as your body. If you want to get some light lifting in, go for it but keep the intensity lower.
If you feel beat to ****, take the week off and chill.