Ritek's quality control is very bad these days, so yes, you probably have some 'B' grade EQUIVILANT discs in there. This is going to become more common unfortunatly, not just in Ritek, but in other brands as well.
Why? Because I can buy 50 4x DVD-Rs for $12.99 (That's Canadian) at a little computer shop in Ontario. Big companies need to compete too, and they are doing everything they can to hold on to their market.
Even Taiyo Yuden and Mitsubishi are starting to have variable quality... although no where NEAR the kind Ritek suffers from currently!
Punch Cards -> Paper Tape -> Tape Drive -> 8" Floppy Diskette -> 5 1/4" Floppy Diskette -> 3 1/2" "Flippy" Diskette -> CD-R -> DVD±R -> BD-R
The Progression of Computer Media