If you only let the meringue sit for a few minutes, I don't think that's the culprit. Otherwise, when piping large batches of meringue, the last tray piped would always be "off" as the batter would be then have been sitting for a few (or more) minutes, and my experience does not bear this out. To me, this looks like an issue of un-dissolved sugar in the meringue batter. Either that, or when folding in the flavorings and chips, you knocked too much air out of the meringue. Lastly, humidity can always wreak havoc with meringues. Are you in high humidity currently?