Fertile days on Glow

Pam • 90s girl • 31 • Married 3 years •
Hey everyone! Yesterday Glow said my fertile days would start today (CD 12) with Tuesday (CD 16) scheduled as ovulation day.
I started OPK testing on CD 10 with ClearBlue Digital and got my first flashing smiley this morning. 
I checked Glow again this morning and found that my fertile days had been moved to start 2 days ago with O day showing as Sunday (CD 14). 
I'm a bit confused as to why it's all changed now. Has this happened to anyone?