I have dealt with this a bit... The Exodus account is two strands mixed together and at first there were 7 plagues.
The story is based on Manetho's History which means if you follow his sources it goes back to legends from early Egypt. Some of the plagues like thunderstorms, locusts, darkened skies, boils and a red river might go back to various events but .... these things happen everyday... no shocker there.