And it is a T5HO fixture for sure? and what bulb strength did you get? What is your distance from bottom of bulb to the branch closest below the fixture?
What calcium powder are you using for the daily feedings?
What are his urates looking like? How are the fecals?
At this age give him as much as he wants. He should be taking down a ton. So if he is not taking down what you are providing then we need to look at the possible issues. Could be size of feeder or the type of feeding method. Could be a health issue as well.
I have a Petco boy.... Just because it is a chain store does not mean you got a dud. Mine will be 4 years old in June so don't feel like you did something wrong in going with a chainstore. They need homes too