There are many and many reasons that can cause recall drops, not all are known, but if it's not for long you don't need to worry, it definitely will be back. Having stable sleeping schedule should help with recall though, and also i suggest lying still when waking up while recalling. Also try waking up right after dream, it is the best time to recall the dream and it can be done by using mantra like "I wake up after each dream and remember it".
Also i suggest checking out this thread: http://www.dreamviews.com/dream-sign...ompendium.html