The loach I assume is Botia histrionica. Get 3 more. They should have a group of 5-6 minimum, and as you have space, another 3 will be good for them. And have lots of hiding spots, they like to be able to select their "favourite". Chunks of wood or rock creating crevices underneath are ideal. I have a group of 5 [originally was 6] Botia kubotai that are very similar in appearance and behaviours.
The other fish ideas are OK, though I would myself not increase the Columbians beyond 7. They and the Diamonds do get largish, and 7-9 of the latter is fine. I'm assuming there are lots of plants.