Do not watch them like a hawk, if this is your first time, just put them in and plan on a min of 2 hours a pd (so if they're 6lb, min 12 hours). It's more likely a 2 pack of pork butts, not shoulder, in in SC, it could be.
You haven't even hit the plateau. Put them both on the same shelf and just let them go.
Outside temp isn't affecting them.