All 3
Positive opk's are usually darker than the control line, maybe you should test every couple of hours after you get what you think is a positive and see if it gets even darker? It's surprising how much it can change in 2 hours and it's easy to miss the surge.
I never get positives in the evening only with SMU which is usually around 11 or 12.
Not everybody's body follows the standard rules, atleast that's what I put it down to!