How is your HC doing now that you have the T5 on it? Mine is also not looking so hot under two stock 5200k light. I was planning on doing the same thing if it wasn't going to be to much light for it.
Looking good though!
What's your CO2 level. It seems like turning UP CO2 has a bigger effect. Try that first and wait for some time to see how your HC responds. It's hard to tell the difference as HC grows pretty slowly at first. If your HC is not melting, that's already a good sign.
From what I read, lighting is not THE factor affecting HC's growth. So I will try playing around with your CO2 for now.