I'm re-tiling for the first time. It's just a small powder room. After I took out the tile, I discovered that who ever had laid the tile had done it directly over vinyl. I removed the vinyl and it looks like there is a layer of plywood in most of the bathroom except for around the toilet area,which has a small section of Ditra underlayment.
My question is, should I remove the underlayment and replace it with cement board (or something) or is it possible to reuse the Ditra underlayment if I clean it out properly (clean out the thinset from the holes and reattach it to the subloor). The Ditra was attached to the subfloor, but the corners came out as I was cleaning the corners. Here is a pic of the area.