Haha, that's what I was worried about when I first started keepin them too!
Nothing to worry about, they are named clown loaches for more than just their appearance! They lie around sometimes looking as if they are resting, usually just because they can. yesterday I found my clown loach under a large rock, not moving and as you could imagine, I was extremely worried, so I put my hand in the water and went to move the rock, but the little guy just un-wedged himself from under the rock and swam away as if nothing had happened.
They are a very entertaining species of freshwater fish and they have alot of character. Most often if they look like they are in trouble they are usually fine, but it doesn't hurt to help them out of a tough situation like under a rock or something.
Another interesting behaviour is "dancing" where a school of clown loaches will swim up and down the side of the tank, from the substrate to the air and back again. It's just their way of keeping entertained I reckon.
But yeah, nothing to worry about if they are just lying around on the substrate or ornaments.
How small is the smaller one? And does he/she have a sunken stomach?