Ovulation spotting or Implantation Spotting

Angel • Sun, Jul 19

Brown spotting yesterday (CD 18) just a couple drops. Noticed it when I went to pee. Glow has my fertile days between the July 11th and July 16th. Had unprotected sex July 8th, 11th,14th,15th and 16th. My cycle lasts 27 days but Glow has it at 29. I'm just so confused. Any input as to what's going on could help. Thank you.