Targets look good. Now you just need to try different loads to really see what makes your gun tick. Ask a few buddies who shoot different shells than you and ask to borrow 2-3 shells or trade and see how they pattern against what you already have. Cheap route and open to variety. That and try different shot sizes, you already shot 6's, try 5's then 4's.
Most guns shoot 5's better than 4's because of the amount of pellets. And don't get caught up in the speed thing. Turkey loads do not have to be fast, just dense!!!! I use a load of 4's as my 3rd shot just because of the possible need to shoot a flying away bird and I want penetration and bone breaking energy. Hope it helps.