yup, could be that too. and maybe slack in the line caused by a back cast that doesn't unroll properly, or a big wide loop in the back cast that has slack in it. Or too early and too hard a pull by the line hand during the double haul, the list goes on. That's why it is always a challenge to correct stuff via the written word--much better of course to see it.
All tailing loops are caused by the rod tip dropping below a straight line path between the start and the stop of a casting stroke. This happens to the rod tip due to a missapplication of power at some point during the casting stroke. Since the line always does what the rod tip does, the line dips downwards causing the line, leader and fly to drop below the bottom leg of the fly line. You can make tails on the forward cast or the back cast and in lots of different ways: using too short of a stroke for the line you have out, creeping (moving the rod forward without any load on it, before the line has straightened out on the backcast), hitting or punching the cast early in the stroke, hitting or punching the cast at the end of the stroke, and so on. All of these are missapplications of power that create tailing loops. Extending the casting stroke and thinking smooth acceleration are good general ways to correct them all.
I'm hoping to get out this weekend and take some speycasting video and if I do I'll take along a single hander and record some tailing loops to put up on the site. I think you'll be really impressed with my expertise at making tailing loops!