There's a sticky on treating skinny loach disease, from the picture it looks underfed to me, possibly previous owner trying either to keep nitrates in check or treating them as scavengers and not feeding them directly. A proper diet and they should fatten up nicely. As far as 14 in a 150, I have 21 in a 180 and constantly looking for more. If the ones you're looking at were near me they would already be in my quarantine tank. Clowns once pass about 4" are really resilient and you'll have time to cure most of what ails them.