Gap on plywood butt joint - Tile Advice

[Ahmad]

Plywood subfloor butt joint Hi everyone, I'm remodeling a bathroom and currently at the tiling stage of the floor. The floor has a 1x5" wood subfloor ( old house) and then has a 5/8 plywood on top. I'm planning on using Ditra as uncoupling membrane but before that the plywood has a butt joint that is about 1/2 wide, how can I fix this? Can I leave this and just tile over it or do I have to patch it with some kinda of patching material? Also the plywood doesn't go all the way to the walls, but have about an 1/2 opening on all sides, is that normal or that needs to be fixed as well?