Thank you for your post.
Pull down the View menu and select "Preview Mode". This is exactly what is being sent to the printer driver. If this is displaying single-spaced, then the printer driver is interpreting the data differently. If this is occurring, then let me know what OS, printer, and version of printer driver being used.
If Preview Mode is displaying the information triple-spaced, then there has been a change to your current layout. Pull describe your layout. It may be that just the Body part was inadvertently sized to a larger height.
Any additional information you can provide may be helpful in narrowing down the possible causes.