Never been to Millbrook myself but I've heard the name come up a few times over the years. A mate of mine who does urban exploring went there about three years back and said he couldn't get a decent photo in that east wing the whole time, battery kept dying on his phone and camera both. He's not really into the paranormal side of things so he just chalked it up to the cold, but I always thought that was a bit convenient as an explanation.
The sanitarium buildings from that era tend to hold a lot of residual energy in my experience. Decades of suffering and confusion in one place, it leaves something behind. What exactly did you feel in the east wing? Was it more of an emotional thing, like dread or sadness, or did you pick up on anything more physical like temperature drops or pressure changes? I find those two types of experience point toward very different things and its worth distinguishing between them if you can.