I think the Anti-poison Shield's skill would probably originally have been poison resistance (medium), but I already unlocked that from the Chimera Viper Shield, so it changed.
It looks like when there are overlapping skills the most effective one overwrites the old ones.
The Medicine Shield has something about a range expansion, but I'm not sure what range it's referring to.
It's either the range a single medicine can be used at or the range that a medicine effects.