Welcome to the forums, learnseo81. I think you are wise not to over-react and to give Google some time to work this out. No, it doesn't sound like Panda.
My one concern was the casual way in which you mentioned adding fresh backlinks like you've "always been doing." It is very possible that Google is re-evaluating backlinks, and they particularly like to devalue backlinks that are under the site owner's control.
Google prefers backlinks that are freely, editorially given from a site that has no association with the link's targeet. For many years, Google has been improving their algorithm to identify other kinds of backlinks that the site owner can create at will - and then to give them less power.