ELO decayed without a warning message?

WTF is this? I logged in today and got a message I was demoted from Plat-5 to Gold-1. I logged in yesterday and there was no message letting me know I need to play any games to stop from demotion. I have got them in the past and played a game to make sure I didn't. This is complete BS. There is only 3 days left in the season and I get demoted by ELO decay with no warning. WTF?