Personally and just in case, i would remove them and place them in salt, and with the "rest in Peace" place if you do it, and replace them with your own protective symbol; like this you do not remove the protection from the house in case that is what they were. I agree that it is too difficult to know exactly of the intent they were used for, so i wouldn't risk leaving them there. If they were to absorbs energy they probably need cleansing anyways. I wouldn't myself reuse them as I find it risky not knowing what they were intended for.
Because of the death happening in the are were they are, i continue to think a 'rest in peace' special prayer or area there would be best with leaving salt there always with smoky quartz.
These energies that try to communicate are really trap for some reason and it is best to help them move on, with kindness of course not to upset it.
If it was me, i would make a Rest in Hope/Peace prayer in my heart, every time a "seeing" would happen, and stay in kindness and compassion for the deceased that is trap; those entities can be very strong and could also be hostile and even make you very ill...mostly if other mediums have assess lots of negative energies there...no joke to play with.
My best advise