Jazz,
I suggest you speed order the hand feeding formula asap. I prefer Zupreem myself but many use Kaytee or etc. ... One should always have some on hand, not only for this Lovie with the current problem but for others if & when they may need it in the future. Just keep it in the freezer to extend shelf life.
An anti-fungal is sometimes prescribed (IME) along with the enrofloxin. You should check with your specialist or avian vet (asap) if one could possibly be useful at this time.
I would also add a second drinking vessel into the cage with Gator-aide or similar in it, mixed about 50-50 with bottled water. I would also be giving the lil tyke a lot of normally relished food choices to include fresh quality spray millet, maybe some corn on the cob (fresh, clean and raw), a quality seed mix, maybe some pellets if he likes those, crackers without salt and anything else he likes. Check with your avian vet or specialist if any foods could possibly add to his problem. Make sure the water vessels are shallow so he doesn't fall in them if he is weak. And as the others have said, try to keep the ambient temp. constant all around his body at about 85 degrees around the clock. Keep perches low and the food & water containers also low.
This bird does not sound like he has any problem that would warrant euthanasia. I would put any thought of that completely out of your mind for now.