Four members of Indigo’s board of directors have abruptly resigned, and the company has announced that chair Heather Reisman will retire this summer.

Indigo Books and Music Inc. says Frank Clegg, Howard Grosfield, Anne Marie O’Donovan and Chika Stacy Oriuwa are no longer on the company’s 11-person board.

In a statement Wednesday, the company indicated that Oriuwa was resigning “because of her loss of confidence in board leadership and because of mistreatment.”

No reason was given for the other exits. “Indigo wishes the departing directors well and thanks each of them for their contributions during their tenure on the board,” the company said.

Company founder Heather Reisman had been CEO of the company for more than two decades until that title was given to Peter Ruis in August. Ruis was the company president at that time.

Reisman was bumped up to executive chair, and Ruis’s old job of president was given to Andrea Limbardi, the chain’s chief customer and digital officer.

On Wednesday, it was announced that Reisman is now stepping down from the executive chair role, too, as of September.

“The time has come for me to retire from an active role at Indigo,” Reisman said. “Deciding when it is time to move on is one of the toughest decisions a founder must make, but I know this is the right moment for me.”

In a separate development, retailer Reitmans revealed on Tuesday that it has hired Limbardi to be its new CEO, starting in September, which means she’s leaving Indigo, too.

Indigo was hit by a cybersecurity incident this spring which walloped the firm’s ability to sell its wares online for several days. Full functionality was not restored for several weeks.