SEP replied to my email as follows:
SEP did experience a larger than normal volume and share price movement one day last week with some partial recovery in price thereafter. We do not have real-time access to the trading information to know who transacted on this date to drive the volume increase. However, there were no SEP company officers who were a part of the transaction as they are required to make a filing with SEC if that were the case, and no such filings were made. Similarly, had there been any new or material news regarding SEP, which there wasn't, we are required by the Securities and Exchange Commission (SEC) to make any material investor information/news available to all investors at the same time.
I have investments in SEP also and track it daily. SEP 90 day average transaction is about 260K shares/day. That day it was 2M shares mostly on the sell side. Not too many SEP individual holders have more than 1M shares to dump. I suspect a hedge fund or another fund type did this to rebalance or change their portfolio at our expense.
I sold immediately after hours based on zero information. When a stock drops over 4% on absolutely huge volume, I sell and ask questions later. It is frustrating for sure. On the other hand, the stock has performed well as of late, that is before today .