All three players were included in England's recent three-day training camp but the trip ended in disappointing circumstances for Tuilagi and Solomona as the pair were sent home early.
The Rugby Football Union said the pair were dismissed from the group due to "team culture issues", although several reports have claimed the two players in question returned to the hotel drunk after a night out.
Head coach Eddie Jones is still deciding whether to punish the duo further and they appear unlikely to be selected for the autumn international series against Argentina, Australia and Samoa.
Hartley, who has had his fair share of on-field disciplinary issues, knows his team-mates made a mistake but he believes they will get themselves back into the good books of the management.
"We're a team and as a team we set our own standards off the field," he said. "And ultimately those guys let us down in that area. We're a team and we've got a code of conduct that we adhere to.
"The team dealt with it and I'm sure those players will have their heads down and be working hard now to get back in the picture. Because they are good players, and both of them are worth having in your side."