My name is ***** ***** I have been a Vet tech for 30+ years with special interest in Reptiles and Reptile rescue. I would like to go further in depth with information for you. The fisr issues I see is that you have the Dragon on Sand. That should be changed to a solid substrate. Loose substrates can cause impations, skin problems and eye issues. I suggest cage carpet, paper or tile. The Diet that you are feeding needs improvement. under a year old we feed 80% live prey and 20% veggies. The live prey should not include meal worms or super worms. They are both high in chitin, which is the hard outer shell, which is not digestible and the super worms are high in fat and over time can cause live disease. The accetable prey are crickets, silk worms, phoenix worms and dubia roaches as staple feeders. They also need 20% veggies to include collard greens, mustard greens, escarole, curly endives, dandelion greens and butternut squash. This is a link for acceptable foods: http://www.beautifuldragons.com/Nutrition.html Over a year old the Dragon needs to reverse the percentages of veggies and prey. He needs calcium 5 days a week and 2 days a week a vitamin.
Temps in the basking area should be 105-110, the ambient temp 90's and the cool side at 80's. The Recommended UVB bulb is a reptisun 10.0 linear tube and it should run the length of the tank. The basking light should be a full spectrum bulb.
You can give the Dragon a dail soak in water at 90* and most will defecate in the water at that time. UVB bulbs do need to be replaced every 6 months since they do loose potency. The open mouth breathing you saw very well could have been over heating because we have to take in temps as well as humidity that could have caused that behavior.
If The Dragon continues to seem lethargic, then a Her Vet visit should be done for a Fecal and a check up. If you need a Herp Vet plase supply a state and I can locate some for you. If you have questions about the information I supplied, I will be happy to answer them. I have been working with Bearded Dragons for over 36 years. I like to supply accurate and up to date information and I strive for excellent servce to achieve a 5 Star rating. Please hit reply for further help.