Samyang updated 4 lenses with improved face/eye AF and overall autofocus performance and you can get the updates here. Also, Most Samyang lenses are still on sale with some savings close to 50% off, which you can see here.
Samyang AF 18mm f/2.8: B&H Photo / Adorama
Samyang AF 24mm f/ 2.8: B&H Photo / Adorama
Samyang AF 35mm f/2.8: B&H Photo / Adorama
Samyang AF 45mm f/1.8: B&H Photo / Adorama