I agree, 50 seems way too cold. I keep my phals on window sills and my house stays about 75 all winter in Michigan. We heat with wood. It's naturally a little cooler near the window but never that cold. I have 8 in bloom right now. The spots remind me also of the sap that a cattleya has. Very strange unless it's from the stress of being too cool. Hopefully someone else will chime in and know what they are.