Hi there,
Really sorry to hear that your Clown Loaches aren't doing so well at the moment, could you possibly let us know your water parameters, when did you last do a water change, have you added anything to this tank lately, if there a no Whitespots then it posslby isn't Whitespot, if it was Whitespot it would look as tho your fishies have been sprinkled with salt, but then again you are saying they are going around scratching on things, maybe the Whitespot isn't evident yet, I would keep a very close eye on them, you say they have White edges around their fins, maybe this is the beginings of Fin Rot, Clown Loaches are really sensitive so just be very careful when treating with any sort of Medication.
Keep us posted as to how they ae doing.
Good Luck
Lynda