Howdy Pure,
Thanks for finding his previously posted info
. Now to get even more details from him along with a ton of photos... I meant to mention photos of the room that the Panther is being kept in would be helpful too.
So beginning the "process of elimination":
Buy an 18" Reptisun 5.0 linear tube and a fixture. This is not so much that you are using a CFL (that model isn't putting out dangerous non-terrestrial UV like some others) or even that it is a ReptiGlo but this is just one of the things that you can do to eliminate a potential husbandry variable leading up to this crisis.
Your "75W basking lamp"... Flood or spot? Try a simple flood from Home Depot like their Philips Halogena brand 60W
flood.
"85F" basking temp. How did you measure it? Optimally, you would use an infrared temp gun and measure your Panther's skin temp. Stick your hand right where he basks and make sure that it feels like a reasonably warm site (especially if you change lights).
"Nights 60-70F". Measure it and let us know what it really is this weekend.
"Humidity gauge broke" Home Depot combo humidity and temp and remote temp for about $15. No excuses

.
"Switched to Hibiscus" Before or after the current problem started? Allergy? Pesticides? Get a different plant and wash the heck out of it and re-pot it. Try Schefflera, they're pretty cheap.
"Crickets". Only? Get silkies and hornworms and dubia roaches.
Gutload with Cricket Crack.
Depending on the detailed info that you provide about exactly how much unfiltered sunlight he gets per week, you may need to increase his D3 to 2-3 times a month.
"Pump mist broke" Electric motor pump mist? At least buy the Home Depot 1/2 gallon pump-up bottle and mist with warm water, twice a day, for 15 minutes or until he drinks.
Photos of his poop and his urates. Not tested for parasites

. You were at the vet's office

. Go back today or send me a sample. Certainly not to point a finger at Screameleons but breeders are susceptible to parasite infestations as much or more than anyone else. For example, a year's worth of Coccidia could possibly do just what you're seeing right now...
"History - He had been relatively fine". We need absolutes here

. Give us the details of his medical life. Any slight deviations from "norm" may be a clue.
Even though vitamin A is not likely to be the problem, you could still single-dose him per my earlier PM and cross it off the list.
Now go back and take those photos and post even more details in the "help" list

. Good luck!