60 and 75% is ideal...
If the humidity tray does not raise it as much as you want, if you direct the fan at the tray it will spread a lot more moisture so one way or the other you will get it up if you want to.
Also when I first set up my case I was using a humidity tray, once my case was set up and filled with 60 orchids I had to start leaving the door open a little so it might be you have too few plants in there
![Wink](http://www.orchidboard.com/community/images/smilies/icon_wink.gif)
Every time you add or take away plants things will change slighly. The more plants you have the more they will raise the humidity themselves.