That is one of the joys of PPrune when it's working well.
What type were you flying? 70 seems high for most singles, particularly solo.
I'd suggest that numbers aside, you may not have had the aeroplane as well trimmed on approach as you needed it to be - if the speed was creeping up, assuming a serviceable aeroplane (I've known the occasional pitch trimmer that crept, but it's unusual, and not usually that fast) then the increase in speed can only be because either the aeroplane's not properly trimmed, or you're inadvertently pushing forwards on the yoke.
G