You have two wheels (rims, tubes, tires) that retain air; and one that doesn't. Your conviction that one tube manufacturer is at fault is unlikely to be the correct answer, as the tube make has changed at least once while the problem persists.

Likewise, it's a stretch to say that tube tires aren't a practical design when the bike is sitting there with two inflated tires. As mentioned before, you almost certainly have a problem with the rim, rim strip, or tire; and when that root problem is resolved, you should expect your third wheel to require no more attention than the other two.

KeS