From dark to light?

Tee • Mommy to an angel baby born on January 22, 2014 at 20 weeks. #AidenLewis BFP 3/1/2015 BABY GIRL DUE 11-5-15
I have pcos and have been using opks since cd8. I'm currently on cd13 and my opk is extremely lighter than yesterday. Is that normal?