Could implantation occur?

Johanna

I started my cycle sept 11-15 according to app Fertile window 17-21 i am new to all of this I have not started ovulation sticks(plan to do that next month if I am not pregnant) bd on sept 19 on September 28 and 29 I had light spotting (could this be implantation)? I am very new to this including the app any help would be appreciated