First of all...I'm not a vet. I'm just commenting about things
that might be worth giving consideration to...or to draw to the
attention of your vet.

Re: herptivite...I never use it that often....but I gutload my
crickets well. IMHO there's nothing wrong with giving crickets
A BIT of romaine lettuce. Its got quite a bit of moisture in
it....and some calcium (.77 to 1, calcium to phosphorous ratio)
and other good minerals and vitamins....but IMHO your gutload
could stand improvement. There is a recipe for a gutload on
ADCHAM that might be of interest to you...
http://ADCHAM.com/html/husbandry/gutload.html

There are some good articles about calcium/D3 and vitamin A
on ChameleonJournals that would be worth reading too....
http://www.chameleonjournals.com/vet/

I don't think you mentioned dusting with calcium or D3...do you
use them? The natural sunlight should help with the D3....
providing that the sunlight is not coming through glass or
plexiglass or such.

If the mouth is opened in a bit of a curve not just simply
being held open...it could be the beginnings of a nutritional
imbalance. Is his arm between the shoulder and the elbow
straight? Your picture is dark...so its hard to see clearly.

You don't mention the temperatures in his cage/basking spot.
Temperature can affect the rate of passage of food through his
system.

Hope some of this helps! I hope your chameleon will do well!