Were there no episodes aired the last few weeks?
It fails to chart even though the bottom are low 3s and going into 2s.
http://www.animenewsnetwork.com/news/2015-08-20/japan-animation-tv-ranking-august-10-16/.91928
http://www.animenewsnetwork.com/news/2015-08-13/japan-animation-tv-ranking-august-3-9/.91639
Decolore was largely hanging around the mid to upper 3s/lower 4s, going through the various weeks.
http://www.animenewsnetwork.com/encyclopedia/anime.php?id=14333
There was a week off, yeah. There's always a slight drop after a week off too.