It looks to be a fine mesh which means the UVB is going to need to be either inside the tank or unobstructed - can you take the screen off or cut it? UVB needs to be directly over a piece of basking decor w/ a distance of 12-15 inches --- your basking bulb is giving off a yellowish hue to it is it the camera? If its the bulb you want a solid clear bright white basking bulb -- examples are Flukers -- Exo Terra Intense or a Arcadia Halogen- I see a analog thermometer in the tank is that the only way your getting basking temps? Please invest in 2 digital probe thermometers -- they are the most accurate for getting surface basking temps- also I would invest in a digital probe hygrometer as well -- placed on the back center wall of the tank --- optimal humidity 40-50% nothing under 20 and over 70% --