Pressed DVD discoloration in collection NEW and OLD

I have noticed on several of my pressed DVDs (DVD-Video SL or DL and PS2 DVD-ROM), ranging in age from a couple of years to a week, some have symmetrical dark areas (although I’ve seen lighter sometimes too) that resemble straight lines or streaks. They are still reflective (not cloudy at all) and you have to look carefully to spot them (might miss them at a glance since they’re still reflective), but the darker areas are there.

I’ve seen some threads about it – one called it staining, a common replication process that doesn’t cause problems (it’s not delamination or “rot”) - I am wondering how many people have encountered this, how many discs in their collection have it, problems etc.

When I do a CD-DVD Speed surface scan, every disc that had the discoloration on the data side came up as 100% good (no bad or damaged sectors) and scanned at normal high speeds (the drive didn’t slow down on these discs to read at all).

Ideas? Is this a common manufacturing defect or am I lucky?sarcasm I store my discs in dark and dry areas and don’t mishandle or bend them (no scratches or smudges, average dust).

I only had one disc with asymmetrical discoloration, it was actually a ring in the middle of the disc (a dark ring), but somehow it played and scanned 100% fine (there was some issues on my TV DVD player however).

That was the odd case, the rest were the symmetrical lines or areas I talked of above and played fine. Anyone else encounter this/have some discs with this that work or don’t?