i also suggest, even though you have a dish in there for water, to soak them in a plastic tub or sink ( if your comfy with that). Just fill it with luke warm water up to around their sholders. This will allow them to soak up a ton of water through their vent ( butt). Because dragons do not usually drink. However it is a great idea to have a dish of fresh water ( replaced daily) in their viv, the reason it is good is it can be an indicator for you. if you see your dragon actually drinking you know he or she is dehydrated.
soak each of them every other day will help them replace the loss of water that happens when they bask. you can tell if your dragon is dehydrated by looking at the little fat pads on their head located behind their eyes. Another way to tell is by their skin.. you mentioned your male is alittle skinny, ask yourself does his skin seem wrinkly? if it does it could be dehydration, and this could affect his appetite. Try running a bath for him...

its worked for me every time. and most dragons really like hanging out in the water, its just when they poop do they want to get out haha...
Oh and separating them is a great idea. its true dealers will tell you whatever they can to sell you them.
Bearded dragons are solitary animals, who come together only to mate, they dont even stay with their babies. They do not recognize kin, friends or anything. if you notice, one of your dragons is larger than the other, some people think its a sex thing, but in reality its a dominance thing, your little guy might not be getting a chance at the food ...but no worries, your a great dragon owner and for serious, once you separate them everything will go just fine.
what I did was a went to target and or walmart. I got two large plastic tubs ( rubbermaid) not the big big tall ones but the ones that are like a foot or more deep and as wide and long as possible. they cost me around 11- 18 $ each, but they stack in eachother and its so slippery the dragons cant climb them. then i have my heat lamps and uvb lamp and the heat pads ( attatched to very thick plexi glass. and i have towels in the cage ( never use sand or loose substrate) and every week i take out the towel pop it in the washer and dry it, and im good to go.
I know separating animals can feel expensive but this is the way i did it, and i travel to and from college and i have beasted through it. Best part is the containers stack which make them very easy to move.
*****the reason im giving this any of this advice is strictly to help you be awesome!
Im not trying to belittle you or put you down or anything.
The internet is such a poor device to convey emotion and tone.
I wish you the best! and i hope you'll post pics and let us get to know your babies