Wow! ten baby beardies is quite an undertaking,I applaud you in your attempt to help these little guys. If you could post some pics of these little guys it might be really helpfull. How old are they? And what sort of condition do they appear to be in, other than a little dehydrated?
Lets see...
first of all I would seperate the babies, ideally each one should have their own enclosure, but if you dont have room for that break them into as small groups as possible. This will help minimize stress, agression, transmission of diseases etc. It will also make it easier to monitor food intake, fecal matter and behaviors.
I would soak all of them in warm water for a few minutes a day to increase hydration.
It would be very useful to get some fecals to the vet to see if they have parasites, of course this is hard to do if they arent eating, but as soon as you see some poopie, scoop it up and send it to the vet. If they were all living together its usually safe to say if one has parasites, they all do, and the vet can work with you on the best treatment for that.
Since you just got them it will probably take them awhile to adjust to their new surroundings. Soak them, set them up in their new homes and leave them alone for a few days. This may make all of the difference.
You can also drip some pedialite onto their noses and try to get them to drink it, this will help give them some energy.
For right now i would focus on getting a fecal sample and seperating them into more managable groups....
im sure others will have something to add as well....
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0.1 Bearded dragon
0.1 mexican kingsnake
1.0.2 Leopard Gecko's
0.0.1 Rose Hair Tarantula
1.0 BTS
0.0.1 Reverse Okeetee Corn
0.1 Bullmastiff
4.1 Cats