Silversword: Thanks.
I am outside the poison area and I can't cure myself. Hopefully this area isn't too big or I will run out of potions Casting heal doesn't help a lot because by the time I am finished the fourth person, the first person needs to be healed again.
It is not a bug. You're supposed to be poisoned throughout that map. When you get to the guy at the end, ask him to cure the poison. Be sure you do this before you follow the other conversation options as you don't want to be poisoned during the next fight.
You should have both rosalind and joseph up to lvl 10 heal by now, and the ability to summon a blue imp. That means you'll have three characters that can cast Regenerate, which counteracts the effects of the poison, so keep on casting that. This leaves only one character (I suggest flece) who needs manual healing, and the blue imp will automatically do that when she drops to half health.