Is there one in particular that has suspicious trading patterns and have you examined it close?

You notice ITG in todays trades? That;s an algo trader but not by stealth. They are not hiding behind a dark pool or anon. They will make life tricky for traders but not impossible. Try charting the NRs to the volume and sp. You really need to be able to male a case for suppression before you go to their management. You also need to have a reputation and or command of a fair number of shares to be taken seriously. If you have that and management ignores you it might be a good idea to research the management and reconsider holding that company.