Why are some tests dark and others faint?

To

So i am about 3 days late for my period now and 17dpo. At 14dpo (day of missed period) i took 2 tests. one was an internet cheapie the other a frer. The internet cheapie (fmu) came back NEGATIVE (see pic below) and the frer (night time pee) was BFP. I took another frer the next day and its as dark as the frer from the day before. So now, a couplevof days later i find another internet cheapie lying around and its so faint. I am like even questioning if i am indeed pregnant.

this top one is 4hh 17dpo internet cheapie.

and these are the frers i took the other day

and this is the internet cheapie i took the other day.