Looks like he deleted the tweet but he wrote earlier that GRA was down with the others while BHS was up. I'd guess he is in RBX and couldn't reach GRA so assumed it was down until they realised that the RBX-GRA line is down.
EDIT: He did indeed delete the tweet, [1] is the url in case anyone knows a website archiving them quickly enough.
EDIT: He did indeed delete the tweet, [1] is the url in case anyone knows a website archiving them quickly enough.
[1] https://twitter.com/olesovhcom/status/928536233311076353