My Hermit Crab Died?!How?PLZ ANSWER?

She just died,her name was Prissy.Ive had other hermit before(Tiger R.I.P,Ginger R.I.P,Daydreamer R.I.P and now Prissy R.I.P)She always had food and water.She wasn`t real lazy so she had good excersise.She wasn`t old.When I had her she only switched shells once she was small.She didn`t need to change shells it was almost too big.But she fited in it very well.What Happened?