#bentspine

Hi i recently purchased a few red fin columbian tetras and noticed one has this curve on its spine not sure what it really is bit worried the fish could be carrying a disease such as the common tetra diesease that will spread hopefully this is not the case. Appreciate any kind of help on this...

So a week ago I bought a female platy. When I bought it it seemed fine, however, it started acting strange and getting really thin. Now, the spine on the fish is bent and it looks in BAD condition. Is this contagious(should I remove the fish asap)? Do I have to put down this fish? Thank you so...