ok .. only been playing a month. havent had to restring the guitar yet. long story short, i took the strings off today. once they come off, should they be replaced or can they be used again?

my low e needs to be replaced. when i bought the guitar i had the shop do a setup on it and they replaced the stock strings with elixir lights.

i want to try a different brand sooner or later to get a feeling for other brands/types....if i need to replace all the strings now because i took them off .. i'm going to try another brand. if i dont have to replace them all...i'm going to just replace the e with another elixir.