The original subpoena was sent Dec 20th 2018 ( and the investigation i believe may have started earlier). The one in May 2019 was a follow up because the person didn't respond by the Jan 2019 deadline.
Also, it was stated in the cover letter in Dec. 2018 the following.
"This investigation is non public,fact finding inquiry.we are trying to find out if their was any violations of the federal securities laws.The investigation does not mean we have concluded that anyone violated the law. Also the investigation does mean we have a negative opinion of any person, entity or security."
A copy might have been sent to GreenGro since they were mentioned as one of the securities the person had.
Just no concern for GreenGro.