Received my first bad performance rating

Got verbal reviews that I was doing great in my 1-1, taking on 3x workload since I was hired. Received commendations from HOD. No complaints, received great reviews from colleagues as well. Suddenly found out I got a "below average" rating post-calibration. With the long hours, increasing workload, and my manager saying he'd rather hire younger, cheaper people in China, I think it's time to leave. Anyone got any referrals? YOE : 10+ TC: 🥜 #tech #nontech