Here I give my thoughts.
I know you're doing good on this. And I understand every concerns of yours from the very beginning. You've been dealing with things from the beginning and you want to be very careful after all.
Now first, this plant looks healthy. May not be %100 perfect but not worse either.
I will suggest something to you. Not too hard to do.
Supply some fresh air first of all.
I know how these bulbs give heat. Move the hot air out from there. Place a fan over the bulbs and send the hot air out from the cabinet. By doing this you'll have passive intake and fresh air in the cabinet. Place a fan to the bulbs to keep them cold and push the hot air to exhaust fan. You don't need to move your lights up if you keep them cool (Or the cabinet).
Air change is much more important than air circulation. (When you change the air it will circulate anyway) So use your circulation fan/s for these purposes.

I didn't like those purple smileys on the form I must tell. There are many and most of them can be gone for $2. Get the cheapest PH meter if you can't afford a digital one. PH strips or PH solutions. They're cheap and will do work for you. Aquarium shops or garden stores must have them. You may not have any PH issue at the moment but you may get it for future. Prepare.

Other things:
What is filtered water? How do you filter?
Do you spray water on leaves?


Get proper answers, confirmations before act. Right now you're not in a hurry.