Re VerVolume on Exporting to Files to disk

For some reason I cannot fathom, GarageBand X has suddenly, unexpectedly, started exporting files to disk at extremely high volume, whenever I export them from GarageBand. (I do mean high!). I have looked at everything I can think of, and cannot find a reason. My first thought was poor gain staging, when recording, but I looked at the volume of each track and cannot see a problem, since I am recording at my normal volume settings, (around 50% of maximum volume on each track), and have never had this problem before, having recorded and exported to disk quite a few tracks, over the last year or two.. It struck me that this seems to have started happening following the most recent iTunes and Yosemite updates, which I installed a few days a few days ago, though I can't think why that might influence this issue...

Can anyone offer any advice? I'd be very grateful if you can help. :-)

ontradio