With a 55# Kodiak and a 400-grain arrow you should have had no problem whatsoever blowing through whitetails. I'd bet you're shooting a lot more energy than my grandfather did for decades (42# @ 26", Dacron string, low-400-grain arrows) and he very rarely ever kept an arrow in a deer.
My first suggestion would be to bareshaft tune your bow. After that, if you feel you need a heavier shaft, load up more arrow weight and retune. But don't use a heavier arrow to compensate for tuning. I'm not saying that applies to you, but I've seen it far too many times.