LP Gains and Loses Problems

Three days ago, I was duoing with my cousin. I've been playing since season 1 but haven't really gotten into ranked until this season. We are only gold IV and are pretty inconsistent (we are both at about a 50% win rate overall). We played 6 games, and two of them had afks. The LP breakdown for each game was:

1st game (normal, no afk): Win 17 LP 2nd game (normal, no afk): Win 17 LP 3rd game (had an afk from minute 4 after he ragequit): Lose 20 LP 4th game (normal, no afk): Win 17 LP 5th game (had an afk from minute 12 after he ragequit): Lose 20 LP 6th game (comeback victory, we were down 20k gold when we won): Win 17 LP

It didn't make much sense to me why we would not only lose more LP in loses than we gained in wins as gold IV players, but also that we lost more LP in loses that were 4v5s for the majority of the game than in a gigantic comeback win (which I know probably doesn't effect LP gains, but it might be a consideration). I know that Riot fixed some of the LP problems that diamond players had in patch 5.10, and I think that the rest of the rank spectrum might need some of their LP problems fixed.