I agree that those arrows are too light for a 60 pound bow, unless you've added weight tubes.

But, getting back to your question, assuming you're right handed... If the arrows are shooting right and are grouping consistently, I'd say you need to build out the strike plate on the rest with a dot of moleskin or leather.

But that's just a generalized guess. I haven't looked at the charts to make a guess on how a 400's spine matches up to 60 pounds, and that could be part of it. There also might be some form issues that need to be addressed as well. Only someone who can watch you shoot could help with those.