Apps just work based on an algorithm. If you were due your period on the 22nd then it’s already late. A pregnancy test would show a positive result by now so best to check.
Sadly I have had a couple of instances of just spotting. Brown blood is old blood that’s taken a little while to come out. After speaking to a gp they said it’s likely an irregular period and can happen from time to time. The following month my period returned as normal.
Best thing to do is to test and find out.