Test experiment I don't get it on 3 test same day

Ok so I will test on Friday again with a first response. Just curious so did a fun experiment I had what I thought was a vvvvfl yesterday morning. Set the test aside and looked at it later out of curiosity it had gotten darker. Evap probably not getting my hopes up. So then set it aside again and now today it's super dark. So again think evap so did the silly put water on it to see if the line disapeard well it didn't. What are your options please. Know I will test Friday and update.