Years ago when we were specifically hunting divers I switched to 3.5", 3 shot. My kill rate was much better and I attributed it to the longer shot string. Pass shooting divers is tough and having a longer shot string for them to "fly through" decreased the wounded cripples. I also learned a lot from hunting on steeper banks and shooting down on the birds. You could see where your shots were hitting both good and bad.
Lesson is, you've got to take time to figure out what works. Investing time at the range or setting up in a situation where you can get feedback, will increase your hunting success and your satisfaction at the end of the hunting day.
It's frustrating to wound the birds, and even worse to lose them. Its great you're looking to get better. I applaud you for it. The birds deserve to be respected and killed swiftly.
God Bless and Happy Thanksgiving.