and welcome to club.myce.com.
Can You read out the mediacode of the discs with Your writing software?
I guess You got Sony Made in India by MBI with MBI-Mediacode in Your last spindle, and the quality has changed for the worse.
SONY DVD+R 16x Made in India with the SONY-Mediacode SONY D21 were decent. Sony Made in India by MBI with MBI-Mediacode might be not.