RE: tuning question
Turning the bow down could help.
Did you move the rest right until you started getting the problem in the opposite direction and then came back? Try that first and then worry about spine.
Depending on your draw length and arrow length the 400's could be underspined.
If you do not have a combination of the following or shorter the arrow is probably underspined:
29" DL arrow shorter than 28"
28" DL arrow approx or shorter 29.5"
Another way to check all of this if you are a consistent enough shot and you have a 50 yd pin is to shoot the 50 at approx 4 yds and sight it in to be dead on and then go back to 50 yds and see where the arrows are hitting. You will also be able to watch the arrows from this distance and see if they are fishtailing and it will tell you more than just having a little left or right nock when you look at them in a target. I thought mine were hitting right and then shot through paper and then out to 50 and everything was dead on.