Refinishing stained concrete and overlay

I had a slab poured a few years back. Then afterwards acid stained and sealed. It looked great for about a year, but now looks like a faded speckled whitish mess. I don't know if the sealer was crap or if it's just age, but it needs some help. So, do I need to pressure wash it off or buy some sort of stripper to rid the sealer before applying a new one?

Also, I have an overlay that was put down over washed aggregate. Also stained and sealed. It has cover on it so It still looks decent, but is somewhat dull. I'm afraid to pressure wash it too aggressively.

Any input on this would be appreciated. I've found some videos on stained concrete redo, but nothing on overlay.