This refers to multiple people so it should read, "You guys eat slowly" or "All of you eat slowly"
Your comment seems to be 'Let's use honorifics properly.' In general, we really need to know who is speaking to whom (= what their social relationship is) and about the situation in which something is said before we can make an informed choice about the politeness / formality level of the verbs and pronouns or other terms of personal reference. Korean has many more formal choices than English, but at this point in the tree, we are only beginning to be exposed to some of them.
My comment was referring to write_your_name's post in Korean, but unfortunately it didn't go in as a reply directly under it.
When the subject is in informal form and the verb is formal form, this can be very offensive saying to another person...This mistake often happens to the korean learning foreigners but between Koreans it has to be careful