Brownish-pink color spotting during ovulation window

Me and my husband has unprotected sex in Jan 12 and according to this app I don’t ovulate until this coming Saturday the 20th. I have never had this before ovulating. I was sick with a cold so idk if that can throw off my ovulation cycle. I’m quite regular with periods too. My period this go around was only like 3 full days then the 4th day wasn’t much which usually I can last 5-6 days. I had cramping yesterday (Jan15th) so marked that in here cause I thought it was odd. Has this happened to anyone else? I’m can’t imagine it’d be implantation bleeding this early.