No worries, most places recommend bloodworms. Recently there have been more and more cases of it contributing to bloating which can be fatal if fed exclusively.
If you DO want to add more, you definitely should quarantine 6+ weeks. (Make sure any and all equipment is kept separate from your current little guy's set up. ) Unfortunately you have no idea what your new frog(s) may have been exposed to or picked up along the way and the chytrid fungus is lethal and contagious. All new additions should always go through a quarantine