Okay for OPK to be positive for only a day?!!

Hello all! Long time member but not sure I've ever actually made my own thread..
Looking for experience and advice- is it okay/normal for there to only be one clear day of positive tests?? Nothing at all up until yesterday, when fmu was clearly positive. Took 2 more throughout day to check it wasn't just a really dye filled test,and they were all clear positives. This morning...a lot lighter...is that..bad?
Tia

Thanks Sugger. X x

Thanks Bev

I tried to do an emoji there and it didn't show up! Let me try again...