You might have told us your setup at the start, we're not psychic
I guess known good disks read fine? I.e. write a disk, read it back, compare - or similar. I guess you're reading Amiga disks written on an Amiga and not with the CW? Were they written on DD disks or HD disks? If HD, is the HD-hole still covered?
Just wondering how you have reached the tentative conclusion that all your old disks are duff.
Tell us more.