I think some additional ventilation is in order.
As a reference, on the type of OH you are using, I have holes large enough to accommodate a regular-mouth canning jar with a feeder lid on it. I put two of these holes on the top, then attach wire screen from the inside. In addition, I have four 1" holes running down each side. If I had thought it out I would have put an 1/8" wire screen bottom board on it as well- good for more ventilation, but also for debris- the bees can haul the debris out of the entrance, but they sure seem to expend a lot of energy doing it.