At 100yds with the results you achieved I'd be assuming there was little or no variation in cross winds. However a variation in fore and aft wind would quite possibly have had an effect on the vertical disposition.
The weight variaition in the pellets may also have had an effect as you have suggested. How much variation is there in the fpe your rifle produces between shots and is it a springer or pcp?
So many factors; if it was me I'd just enjoy the results achieved and have another bash.
Jim
ps Which biscuits come in an 18" tin?