Alan Murphy wrote:

My question is: is this all in my head? Can CD damage due to excessive
heat manifest as a loss of fidelity? Hopefully someone here who has
expertise in these matters can help eliminate my fears.

It's in your head. Damage to CDs is digital in dature - that means,
either it can read the data stream or it cannot. Sound "quality" is your
ears, speakers, and amplifier. Also, the temperature of the room and
ambient noise can make a huge difference. Perhaps the room just needs
a good airing out?