It sounds as though the seven sisters were hacked to death by a crazed woodcutter. Sadly a lot of that went on in the 19th century. They will continue to haunt the scene of the crime unless you take action.

Without a doubt you should get an exorcism. Genuine exorcists are hard to come by so you'll need me to set you up with one for a 200% finders fee.

Do not accept psychiatric intervention. The drugs could make you so drowsy that you won't even notice an axe wielding nutter until the blade of her hatchet is embedded in your skull.

In the meantime, there is no need to vacate your flat.