"Jeff Wisnia" wrote in message

Check to see if your toilet supply was plumbed to mix a little from the
hot water supply in with the cold to prevent a tank full of cold water
from sweating on the outside if the humidity is high.

It might have been done that way and has gone out of adjustment.

That brings up another situation. If a faucet is shutting off flow to the
sink, but leaving an opening between the hot and cold chambers you could get
a mix also. Since the toilet is on the same line to the bathroom, it may be
getting a dose of the hot water. That situation came up here a few months
back.