Please help with my opks so confused!

I have a regular 30 day cycle so today would be spot on for a positive opk.. took one this morning (darkest one at bottom) even though it's dark it's not quite there... But just took another now at 8pm and it's gone very light again! I was expecting a full blown positive 😏 ant chance I could have surged last night and missed my peak.. hence why I only got a faint positive this morning ?