Did you bring these clips in a linked? Or did you Store local copy?
Also, is your Archive set to Linked or Stone?
a Linked archive will be very small. As it just links to the files, but on Stone the Archive will want to hard import all of the media... as DPX. This is probably why you are getting such a size bump.
DPX frames are uncompressed and I am guessing that your QT's are of some compressed format.
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