en_tn/act/15/30.md

so they, when they…after they…they delivered

"they" refers to Judas, Silas, Paul and Barnabas

were dismissed

" were given permission to leave" or "were sent away"

down to Antioch

an elevation change. Also, away from Jerusalem, regardless of elevation in the final destination, was "down"

they had read it, they rejoiced

"they" refers here to the Gentile believers in Antioch.

encouraged the brothers

"encouraged the believers at Antioch"

also prophets

being a prophet carried authority from God in a special way. This may be translated as "because they were prophets" or "being prophets" UDB.