Chrome distrusted Symantec certs when 70 got pushed to stable (at the end of October)[1]. Digg shows NET::ERR_CERT_SYMANTEC_LEGACY error when I navigate to it. Firefox was supposed to remove the Symantec certs in 63 (also to be released at the end of October) but I guess they pushed it back a version[2].
All major browser coordinated to distrust the certs at the same time.