One app says I start ovulation one day and the other another

Fanistar • 2 boys ⚽️ and now a girl 🌸 My husband ( who wants an open marriage now that we had our baby 😤) and I have been TTC since late August 2017. Had a miscarriage in February 2018. Found out I was pregnant again at the end of March 2018. I'm broken but happy I

Glow says I start ovulating on the 12 and actually ovulate on the 18. My other app says I start ovulating on the 14 and actually ovulate on the 19.... 😩 I will be taking ovulation test everyday. My period was Oct 3. Anyone going through this? I don't want to take any chances.