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Bright heater unusual, but not necessarily bad. If the plate of the tube was glowing that is BAD very bad...Redplating occurs when a tube is passing far more plate current then it is designed to handle. This occurs in rectifiers when there is excessive load, and in triodes/tetrodes/pentodes when there is either too much load or more often when the grid bias is wrong. Redplating usually destroys tubes in seconds to minutes, and should not be allowed to occur for an extended period of time unless you enjoy paying for replacement tubes.
A redplating rectifier is probably a symptom of a B+ short, shorted lytic, or some stage HEAVILY loading the B+. If you have it you need to fix it first before anything else. A DMM/VTVM/VOM is your best friend if the source of the fault is not obvious.
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