Help, app saying I ovulated on the day I got peak ovulation test

Ive been using the natural cycle app alongside flo app and tracking my BBT via NC. On 19th April I had a positive ovulation test (smiley face on clearblue) so I thought i was at my peak pretty much, however the NC app has moved my ovulation date from 21st to the 19th because of the rise in my BBT and because iv logged a new period three days ago. I had a smiley on 19th and 20th April so my guess is I ovulated on 21st. Any ideas? Im currently on my period now (day 3) so want to get it right for this cycle!