User blog comment:Omega natsu2/Chapter 397: Steel, Predictions./@comment-77.195.192.19-20140825072802

It seems there is an explanation on mangahelpers about the delay. Editors changed the day of shipping of their magazines to stop scanlations :

http://mangahelpers.com/forum/showthread.php/2997848-Fairy-Tail-396-Discussion-397-Predictions/page5