DWARF SKINK
Mabuya Plainirons
Adult reach 6 inches in length
They are a ground dwelling species, found on forest floors and rocky steppes.
They prefer 77-86 Degrees during the day
90 Degree basking spot
68-70 Degrees during the night
In captivity they require a full spectrum fluorescent UV Bulbs
You have a good size aquarium for them, coconut bark is fine, make sure you have a few hiding spots for them and just give them a misting one or two times a day. You are dusting their insects with vitamins already which is good, dont dust the insects everytime though, try every other feeding or once a week ( depending on how often you feed them. }
I bought a few of these guys several years ago and also did not know what they were and neither did the petshop, they were in a tank of several species of lizards, I liked them bought them and then looked and researched everywhere to find out what they were { hence forth found out the were dwarf skinks from Africa }
Your set-up sounds fine, good luck!!!!