That sounds totally confusing. I'm having my own issues with cheap OPKs so I understand!!!

Do you happen to know the sensitivities of the different tests? Like, what LH concentration is their detect limit? If they are the same, then I would guess that you're just borderline +. If they are different, then one of the tests is faulty.
I would say, a + is a +, so carry on as if it is a surge!!! But keep testing to see if you get unequivocal results later today or tomorrow.