Do pregnancy tests get lighter the further along you are?

I’ve heard that as your pregnancy progresses, your test lines get a little lighter especially if using fmu. True?

Because I’m just about 8 weeks and mine are slowly getting lighter. I had dye stealers when I first took the tests at 4 and 5 weeks and now both lines are the same colour. I’ll add a picture. All tests taken with fmu.

Test below was taken today, not with fmu but with second pee of the day. Should I be worried?