Why aren’t they the same?

I have been taking first response and easy home ovulation tests this month. I have already had a positive surge with the easy home. When I was getting positives with easy home 2-3 days ago, first response tests were still significantly faint. Now I am getting negative faints on easy home and positives on first response. Why are they different. One says I had my first surge 3 days ago and another says I’m having my first surge today. How do I know when I ovulated. 3 days ago, or now? Please help! Has this happened to anyone else??