Since they weren't all from the same urine sample, it's hard to say -- FMU is more concentrated, so it's most likely to give you an early positive than later samples during the day.
However, because the only positive test did not turn positive until outside the "read" window (I think you said the directions said 3 min, and it turned at 5), it could very well have read positive without you actually being pregnant. Not technically a false positive b/c it wasn't during the prescribed window.