2020 error?

I played summoners rift ranked solo and duo first round of season 2020 and I was 6/3/3. Our team lost but I thought I did well. Other teammates had a bad KDA than me. My friend got 0/7/6. I got iron 5 and my friend got iron2. I think I played well but why did I got iron 5? I had higher damage than my other teammates. I think I should go to the higher rank because I did better other players, I got the lowest rank. Can you guys check if this was an error or just I had bad luck and got iron 5?