Could 1/4" impact spine that much?

I have 2 identical arrows (Beman Speeds) except one is 1/4" shorter...everything else is the same. The shorter (lighter) arrow was hitting 2" high and 2" right at 30yds. I added 15 grains to the lighter arrow (85-100gr field tip) and now it flies great, just a little low as compared to the first arrow). Seems to be more forgiving (I am guessing b/c of the better FOC).
Any thoughts?