I'm curious do yo girls get evap

Evaporation test in all of brand of pregnancy test blue dye pink dye because a get evap line in all brand. And it look lake a faint positive with color. For example if i do 10 pregnancy test of different brand I will get faint line in 9 of then around 20 min mark or 10 min the more it dry the more color I see. Is this normal. This is happening to me 4 month ago never happened before if a get a negative negative will stay but know turn positive any idea. Thanks😩😩