Did you say the DB8 was for VHF? Is this the antenna?
http://www.antennasdirect.com/store/DB8_HD_Antenna.html
WMUR CH9 might be too low for this UHF antenna. The other VHF station you mentioned, WENH is ch11, higher in frequency, has a stronger signal than WMUR and is being picked by by the XG91 if I understand your antenna positions correctly.
Antenna located in the attic doesn't help either.