Actually, I just took a closer look at 1by-day, and they are not dropping in video quality, they have just stopped updating altoghether, recycling old sets as new...
Normally, each week has 6 new sets and 7 old remastered sets, with the remastered ones clearly labelled. This current week had just 1 new update and 12 old sets (where only 7 are labelled as old). Next week's first three planned updates are all old sets.