Ovulation strips

Chloe

Hi guys! According to my apps I’m currently in my fertile window and I’ve been taking opks every day. I haven’t had my positive yet but I was just wondering if it’s normal that yesterday’s opk was a lot darker than todays? Both were still negative as they wasn’t matching the control line however I’m just curious as to why today’s is a much fainter line.

Any help would be fab💖