"¿Ustedes están cansados hoy?"
Translation:Are you tired today?
I have had many sentences in duolingo recently where ustedes was translated as all of you. My answer should be accepted.
"Y'all" is a regionalism and so should be recognized as a word that some people use. I, myself, prefer to use "all of you" when translating "ustedes," even though the pronoun "you" is both singular and plural, as well as being a subject pronoun and an object pronoun. I use "all of you" in translation because it is less objectionable to native Spanish speakers, who have a hard time remembering that the English pronoun "you" does not need clarification.
In normal speech, the inflection rises at the end of both Spanish and English sentences.