Kerbal Space Program

Not showing fuel on all tanks is normal for symmetric parts. Only one gets the label.

But I am seeing the behavior you describe, for the most part. One tank drains while all three engines fire. After that tank is empty, however, both of the remaining tanks drain as one would expect, and the engine on the empty tank no longer has a supply (as expected).

Oddly enough, if you eject the initially draining tank in the middle of the three-engine burn, it still feeds the other engines until it's empty, even while detached from the ship.