The phrase "Ellos están muy cansadas" contains a gender agreement error. "Ellos" is a masculine plural pronoun, so it should be paired with a masculine adjective. The correct form would be "Ellos están muy cansados" if referring to a group of men or a mixed-gender group.
If you are referring to a group of women, you would use "Ellas están muy cansadas."
So the corrected versions are:
- For a group of men or a mixed group: "Ellos están