Help with digital

I know it makes it invalid and I'm not here to get moaned at for this but...

I have used clearblue digitals twice this week (3 days apart) and both times they have said not pregnant.

I took them both apart and there has been a colour change on the strips though, is this of any significance?

Top is today and is darker, bottom is a few days ago.

I live in China and ran out of tests and I have some on order but it's been 5 days and they've still not been delivered. I'm due AF tomorrow and I just want to know!!