Lets average the temp out so you have loosely 83-4ºF ambient air thought (heat lamps project IR down and heat the temp probe so it is an artificial increase)

83ºF has a saturation point of 28 gm/m3 (average again) 49% of 28 is 13.7 gm/m3. Following? Royals need around 15.5 gm. You are low. For and ambient of 83ºF you should target 55-6% RH (55% of 28 is 15.4)

80º has a saturation point of 25.38 (so 60% is 15.3 make it an easy number and 15.5gm/m3)

Here is a list,
Temperature (ºF) - saturation points
74º - 20.98
76º - 22.37
78º - 23.83
80º - 25.38
82º - 27.00
84º - 28.71
86º - 30.51

Here is a graph... sorry my cousin is an underwater welder and scuba guy so the chart relates to that.
http://www.scubaengineer.com/high_pr...or_filtrat.htm