He's not a pygmy dragon, either they lied about his age (most common) or he's very stunted in growth with the terrible care he has. Not your fault really... you didn't know any better to not listen to such a terrible place, most new owners don't realize how bad petco/petsmart are.
At only 7 grams he's very underweight if he was 4 months old. Most dragons are well above 30 grams by then.
If i were to guess his actual age I'm gonna say 2 months old not 4 months. The lady most likely lied and he was probably just a few weeks old when you got him.
Make sure he has the following,
UVB - Reptisun T5 HO 10.0 22"
UVB bulb and reflective fixture with either nothing or only screen blocking the bulb, bulb replaced every 6 months.
Heating - Bright regular basking bulb that isn't colored (red, blue, green etc).
Proper substrate - Tile, paper towels, non-adhesive shelf liner or repti-carpet. No sand or any loose substrate.
A proper way to monitor temps - This can be a temp gun or a digital temperature gauge with a probe. Stick on gauges do not work at all and can not be used.
The temps sound good as long as they are being monitored with what I listed above.
At his age he should be eating 3x a day, 10-20 bugs at the very least every feeding.
Here is a feeding guide.
Do note the 10-20 bugs a feeding is a minimum, most do how many bugs they will eat in a 10-15 minute time frame.
All life stages eat 10-20 bugs a feeding.
1-4 months 3x a day.
4-12 months 2x a day.
12-20 months once a day.
20+ months twice a week at the least, every other day at the most.
Staple feeders - Crickets, locusts, grasshoppers, silkworms, black soldier fly larvae, dubia roaches, turkish roaches.
Treat feeders - Waxworms, hornworms, superworms, mealworms, butterworms.
Wax worms - once a week, 4-5 max.
Hornworms - every other day to every two days, 4-6 max.
Mealworms - every other day to every two days, 5-10 max. Only for beardies above 6 months.
Superworms - once or twice a week, 3-4 max. Only for beardies above 12 months.
Butterworms - once or twice a week, 3-4 max.
Daily greens- Turnip/collard/mustard greens, endive, and kale if added to a mixture of the other staple greens mentioned.
Fruit once or twice a week - Banana, strawberries, blueberries, blackberries, red raspberries.
For more food items -
http://www.thebeardeddragon.org/bearded-dragon-diet.php
http://www.beautifuldragons.com/Nutrition.html
Supplementation -
You want two supplements at the very least, a calcium and a multivitamin.
I recommend the Repti-cal brand but zoomed is also good.
The supplements should be lightly dusted on all bugs.
Generally, beardies below two years need calcium 5x a week and multivitamins 2x a week.
However, beardies above two years or at two years of age need calcium only 2-4x a week with multivitamins 1-2x a week.
This does depend on how your beardie is with diet, health, just laid eggs, is laying eggs, etc.
Did you guys do a fecal test to comfirm he had parasites or did he just give him the meds?