I think it's the same family. Plumbers were often tinsmiths I believe so apart from the ages, everything else fits. I think also that Margaret, one of the children of Maria and Alexander moved into the home after they had both died with her husband.
So, I'm now looking to find Logan links with Ballycorr and Ballyeaston as well as Stewarts.
Thanks so much all of you for your help. It has saved me going round the bend... for now!