I'm afraid my bearded dragon, Luna, is getting skinny. The sides of her are wrinkly, and when she lays down her stomach looks like nothing's in it. I feed her 5-7 supers a day and offer greens every day. She is in a 40gal with a 100w bulb and a reptisun 10.0.
Sounds to me like she's being quite underfed, especially for that length. My girl is 6 months, and last length a week ago was 17"... She eats about 10-15 supers in one sitting. Depending on the day, she'll get fed a 2nd or 3rd time, usually with a different worm. My 4 month male also eats quite a bit...smaller supers, and more soft-bodied worms, but still a lot of protein.
Always keep greens available, but you may want to start trying to feed her more often, and make sure it's dusted with Calcium w/ D3. If she's picky on supers, try Dubia's, BSFL, and some treat worms like butterworms, and hornworms.
Try to feed more, and keep track of her weight every few days.
I use a kitchen scale, in grams. Whatever you have will help...units can be converted. A kitchen scale, postal scale, etc. Something that's capable of measuring more accurately than just pounds, like a scale for a human.
Superworms are not a good staple food. Should only be fed to adults as treats (twice a month or so) 2 or 3 at a time. Their exoskeletons are hard to digest and, lack proper nutrition. Try crickets, dubia roaches, BSFL or, silkworms. These are all good staple bugs and, high in nutrients. Dragons get their hydration from bugs and, salads.
You dragon sounds a little dehydrated to me. Try puting drops of water on his snout with an eye dropper, keep doing this until he licks it off. Or give him a bath, some dragons will drink from it.
At 16 inches long , I assume he's maybe 15 months old .... ?
If between 1yr and 2yr old , I give one meal of insects per day + greens.
ie today Peppa and Toothless , who are 1.7 yr old , each had
1 x LARGE silkworm
+
12 medium crickets (gutloaded with bchoi & carrot) , they both love their crickets and would lots more if I offered
+
some greens.
Took them each about 7 - 8 mins to eat all that.
I give superworms at most twice per week and never more than 2 - 3 each per session.