I had two cases.
One of them being the smallest loach out of three, was really skinny and eventually died.
The other one was the leader of the three, but the other loach outgrew it really fast and started to bullying the other one, so the leader became really skinny.
At this point I introduced another 3 small clown loaches, was an instant improvement, the skinny one quickly put on weight and is not almost as big as the biggest one.
Out of the three new ones the smallest one, much much smaller than the rest, only about 2cm long, unfortunately died, it could never get enough food and often had broken fins and tail.