You're not alone! Many people have left/sold their LEDs and went back to the real deal!
MH and/or T5s will be great, as we know. Remember to adapt carefully your system to the new light when you do it!!!
You can find 20" HOT5 fixtures. Only 2" more…
I think the 250W Radium does a great job, but the T5s would be really good too and more uniform.
I had a 55gal in the past with 2 X 250W MHs and 2 NO actinics. Never had zoas growing faster and healthier than that!! Too bad it was really hot and I couldn't afford a chiller.
I would remove the GFO and feed less frozen food to the system.
As I've told you before, the dry coral foods do a great job and they won't add phosphates and other things to your system, like the frozen do. Also for the fish, dry food. You can give them some boost sometimes with mysis or so, but not a lot.
Please make sure you check the Ca sand alk every now and then, to see if the numbers are kept in balance. Apex must be really good!! I have Reef Keeper and like it a lot. Some say Apex is even better.
So it could be that your GFO is affecting the zoas, considering that the tank is well maintained, no pests, algae, infections, predators and all params are great.
I would try to keep the temperature around 79/80°F.
Grandis.