It's not unusual for a company to change the formulation and kill a bunch of users. Maxell went through this a while ago. Ritek was making their disks and they worked just fine. Then Maxell started coating their own and their reliability went into the toilet.
Ritek-Ridata still makes the original formula (so far) and that has worked pretty well.
We use Sony exclusively, but it's not printable.
You can use a program called "DVD Media Inspector" to figure out what you have. If you have any older stock left, I bet they have a different signature than the newer disks.
Koz