I apologize, I think you got confused and wrote "Amazon said the Zillas are delayed" by accident, and that's what completely confused me, I hoped you hadn't ordered more Zillas!!!
Did you remove the clear cover over the Zilla fixture? I've never heard of the Zilla Desert 50 UVB tubes causing any "issues" or "problems", other than they are far too weak and dragons develop severe calcium deficiencies and MBD because they don't provide nearly the
UVB light they need, especially with those damn covers on the fixtures that block all of the
UVB light emitted, so I think most of this is the lack of UVB, and I'm thinking that as soon as the Reptisun tube is shipped to you can you get it on him he'll perk right up...I forgot to ask where you live? If you live anywhere warm (or where it's at least in the mid 60's or higher) you can always take him outside for an hour each day, an hour of direct, natural sunlight is enough to really help them.
It's good he's eating, some of them won't eat greens/veggies at all, even as adults, they just don't get it I guess, but as long as he's eating on his own at all it's a really good thing, and it's a big deal because most dragons at this point with no proper
UVB light would have stopped eating long ago. So that's awesome...
Damn Christmas shipping, that's the delay I'm sure. As long as he's eating just keep dusting his bugs with calcium, keep giving him fresh veggies/greens in case he decides to eat them, and keep him
hydrated by mouth by offering water or Pedialyte on his snout several times a day for him to lick off as much as he wants to...or if he does actively drink water through his mouth in a
bath, then you can try that once a day too, though if he doesn't drink through his mouth then a
bath does not offer
hydration.
If you think the Zilla Desert 50 UVB tube was causing actual problems beyond just too low an amount of
UVB light, then you should turn it off. Again though, I've not heard this about these tubes. I actually have several friends that insist on using these on their dragons, and they are all perfectly healthy with excellent bone density, proper growth and development, etc. But they both have obviously removed the clear plastic safety covers on the Zilla tube fixtures, strapped the entire fixture to the underside of the mesh lid of the tank using long, plastic Zip Ties or Wire, and have a Basking Spot/Platform that puts their dragons within 5-6" of the unobstructed Zilla tubes. They also replace them once every 6 months on the dot, which you'll have to do with the Reptisun 10.0 T8 UVB tubes too (I don't remember if you ordered the T8 version to fit into the Zilla Slimline Fixtures you already have, or if you ordered the much stronger T5 version and a new T5-rated fixture for it).
Be sure those covers are off the Zilla Slimline fixtures if you ordered the T8 strength of the Reptisun 10.0 T8 tube and are planning to put it in the Zilla fixtures you already have, because it too would be totally blocked by that clear plastic cover. Be sure that you strap the Zilla fixture to the underside of the mesh lid so that the Reptisun 10.0 T8 tube is not obstructed by the mesh lid either (it's only 2 watts stronger than the Zilla Desert 50 UVB tube and still cannot be blocked by the mesh lid), and be sure to get his basking spot/platform within at least 6" of the Reptisun 10.0 T8 tube...If you ordered the T5HO version of the Reptisun 10.0 and a new fixture for it, then it can actually sit on top of the mesh lid (no plastic cover on the fixture though, so if you did order a new T5 fixture be sure it has no stupid cover on it), and the T5HO only has to be within 11" of his basking spot/platform, and only needs replaced once a year. I'm sorry I don't know which Reptisun 10.0 UVB tube you ordered, but rest assured that even though the T8 version of the Reptisun 10.0 is also pretty weak, as long as it's not blocked by a mesh lid or a plastic cover, and is within 6" of your dragon, and is replaced every 6 months, it will certainly not caused him any damage and will be completely adequate for him.
I'm taking note of this situation with the Zilla Desert 50 UVB tube, as obviously the main problem was that the plastic cover was blocking 100% of the
UVB light, but the fact that you removed the cover, had it mounted under the mesh lid, and it still was causing him some problems is something to take note of. I've not heard of this with the Zilla, but rather always with the All Living Things and the ReptileOne brands (PetSmart house brands, they're complete rubbish), they are known to also emit harmful light rays that cause eye damage, neurological damage, and even blindness, and these light rays seem to be a by-product of the cheap manufacturing process. There's a ton more of these brands, I could list for hours, but All Living Things is a huge, popular brand (unfortunately) because it is PetSmart's house brand, just as Zilla is not Petco's house brand. You'd think they would choose a high-quality brand of reptile lighting and supplies to be their house brands, like either ZooMed/Reptisun, Exo Terra, or Arcadia, but no, they pick the cheapest, chinese-made, mass produced garbage...it's upsetting.