My nitpick, and this is a common occurrence in shows about ghosts, is if the ghosts have no physical properties and normally do not interact with materials in the living world, how was it that they made impression on the couch and the cushions? Specifically we could see that the deflection on the couch when they sat there.
Also, this has been raised before, are they not supposed to be in the outfit of their death? Trevor does not wear pants, Pete has an arrow across his neck, but Isaac, Alberta, and Hetty are all in their dress clothes. If Isaac died of dysentery, he is likely to have die