MIA Center Controller reported a loss of separation between to IFR aircraft.

Narrative

Aircraft X was a PBI lander on the SHRVY1 arrival. The Pilot checked on with normal speed until RACNO; then published speed. The Pilot asked for normal speed along the arrival; to which I approved until TARTY (the PBI boundary fix); then published speeds. Aircraft Y was a ZZZ-TPA flight at FL180; on course.As Aircraft X made the turn at RACNO; the conflict alert began to flash. Aircraft X was already leaving FL190 in a descent per the arrival; and the separation was not lost at this point. I asked Aircraft X to expedite through and report leaving 17;000. I then called the traffic to him and asked him to report Aircraft Y in sight. He reported the aircraft insight as he entered the 3 mile bubble around Aircraft Y. I instructed him to maintain visual separation to which he responded with the appropriate response. No further incident occurred between these aircraft.This was a mistake on my part. I had a hoop on Aircraft Y specifically for this traffic and didn't get back around to Aircraft X to stop him due to the volume of the sector. I need to be more proactive and attentive with the low flights that cross the SHRVY arrival.Fatigue likely played some role in this event as our entire area has worked incredibly hard and for many hours during the holiday week. We've also had many controllers out; lowering our staffing even more. This is in no way an excuse for the error; merely a factor.