I found some white specks on the Blue-tongue's head scales... are these mite faeces?
They're at the black strip, next to his eye.
Can't get any pics, but they're also on his back.
Agreed. What was recommended to me years ago by a wildlife carer was flea powder+pillow case+ lizard. She swore by it I am unsure about its actual effectiveness but this could be a cheap option or if you just can't find the other stuff. Also mites will spread to your frogs so I think you should wear gloves when handling any of your herps.