Lines lightening

Alissa

I got faint positives yesterday with a One Step Rexall blue line test, and a cheap pink lined brand, at 11dpo. Today I retested with a First Response and it looked negative. There may have been a very faint line, but it could have been my eyes wanting to see it. Is it normal for lines to lighten up? Or maybe I had false positives on 2 other tests?