Thanks, VGMDB shows that another one is coming on September, don't know if it's the second Volume of the OST or just tracks from the special episodes.
Out of Tracks Vol.1 27th July & Vol.2 September 28th, yes they are soundtracks that didn't make it on the official released soundtrack 27th July also which will be included as bonus with DVD Vol.1 & Vol.2 more info
here (
http://www.animenewsnetwork.com/encyclopedia/lexicon.php?ann-edition=uk&id=74) about different soundtrack release if your unsure.