[Boris]

Hi Ken,
I think your humidity sounds very good ... even a bit dangerous for getting fungus and root rot. Temperatures around 18° C are ideal conditions for all sorts of fungi. You should provide a good air circulation (better invest in a neat fan than a humidifier) and lots of light with this high humidity to avoid fungus attacks. In my highland basement room I've got at daytime humidity of about 50's to 60's and at night about 80's and for example hamata, lowiis, ephippiatas and aristolochioidis are thriving. Only my rajah isn't doing well but it never did. But I'm quite sure that it isn't the humidity ... don't know.
Also don't trust cheap hygrometers. Those can give you an idea about the humidity but often are far away from the right values.