Welcome to Fishlore!
Loaches especially clowns are very sensitive to water quality. Please tell us your
ammonia,
nitrite and Nitrates readings. Also what kind of testing supplies are you using.
16g is too small for the Clown Loaches alone as they are heavy waste producers and need lots of room to swim. They also need lots of hiding/sleeping places. your Clown Loach could very well be reacting to that lack of space.
I love the different stripe patterns

What is in the 140g that would eat them? Let us know how they are doing.
Carol