I've kept the humidity around 70% for the whole time
Have you done major modifications to the tank?
Tanks in general have a very tough time holding in humidity, I have never seen one reach 90% and even 70% is usually not attainable for more than very short periods of time.

A dent in the eye ball is typically caused by low humidity, when you say it's been 70% it makes me wonder what you use to read the humidity?