Opk help?

I’m not sure what is going on this month. I normally have a cycle that’s about 30-32 days. This is my third month really tracking with opks and the last two months ovulation was very clear. This month I’m not sure what is going on. When it’s clear it reads well over 1.-whatever, this month they aren’t getting super dark but are not light still either like normal before and after the surge and peak. The last two months I ovulated on days 18 then 19. Does anyone have any idea or similar experiences? I understand times are not exactly the same but they are all with a few hour long hold and when I had a chance to use the bathroom at work or when I was home on weekends.