"You have the suits" can be translated as plural "jullie" or singular "jij", and both would be perfectly valid.
Duolingo MUST indicate, when asking in English, which of both they are referring to, otherwise this is a waste of time.
Wasn't it? Perhaps it has to do with the fact that there's no contrast, therefore there's no need to use the emphatic pronoun. Anyway, I wouldn't say it's wrong per se, unless you were doing a 'type-what-you-hear' exercise.