Earlier quoted context omitted.
The word medium comes from latin, its plural is "media", not "mediums".
I’m ESL, how far should the “thou should pluralize a loanword as it was in the original language” rule go? It seems to be not universal. I mean, it’s “hamburgers”, not “die Hamburger”, “robots”, not “roboti”, and “rubles”, not “rubli”/“рубли”.
The basic rule of thumb is: assume it doesn't apply. That is, for most foreign words, -(e)s is usually an acceptable plural word, and even if it isn't, people will understand what you mean.