Cold Shower

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What can be done, if anything) depends upon how the hot water distribution pipe to each shower is plumbed, and whether or not you have temperature/pressure balanced shower faucet in one, the other or both showers.

From here it sounds like a misbalanced temperature/pressure valve on one or both showers…and these can be adjusted.

But without more details is only a guess.

Best approach is to have a professional look at your system.