Why has my spider changes from black to gray?

wat kind of species is it i hav alot of spiders and im only 12 not taratulas but i hav exsperons it probaly molted if it is not eating or moving around as much then it had molted and its body is very fragile.but i hav to warn u dat u do not put in another spider because if u do u wil hav to say bye bye to ur spider because when spiders are molting they leave them self open to attack are very fragil they dont eat and after molting give them som time and they wil be hunting purfectly