Cold isn't

My 2 story house was plumbed in 2015 with PEX throughout and all new fixtures. Recently the cold water from several faucets has been been coming out quite warm. I measured it at 93ºF full cold. Other faucets were in the low 50's. Absolutely no changes have been made to any of the PEX runs, no faucets repaired or replaced, no changes at all. What could be causing this?