changed rest - sight marks dropped- why?

[ec]

i moved from a plastic rest that supported the arrow in front of the button to a single wire rest that supports it behind the button.
i redid my knocking point so that the bare shafts hit in the same place, in relation to the fletched, as before.
However, while the distances between my sight marks are unchanged they are all lower, by 4mm. I would understand this if i hadn't redone my nock point. So im a bit muddled :(
is it a common fact that a support more in front of the button will give a 'higher' sight mark for a distance than one that is behind??? :scrambleup: thanks

[crosshairs]

What I think is that a plastic rest is non collapsible, while the wire rest, being collapsible, has less tendency to give the arrows the extra support to propel them to greater heights.

What do you guys think?