The particular spot where all 3 antennas have been mounted is evidently a high multipath area. There is something near that spot that is reflecting signals, therefore the quality of the signal reaching the TV(s) is poor.
Either one of the 3 antennas should work well if placed in a area where signal reflections are not an issue. I have noticed that signal quality is poorer when the antenna is very close to the roof in some instances. The antenna will likely need to be re-located. As you have noticed, the reflections can kill reception of even robust signals.
If this were analog TV, you would be getting the problem stations, but would see severe ghosting in the picture.
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