What is causing Zedd and Addie a problem, what does Zedd try to do about it and what happens when he does?

Zedd and Addie are beginning to deal with the sickness that the skirn has caused with the wound it gave Addie. Zedd tries to heal Addie using his wizard's magic. When Zedd touches Addie with his magic, the sickness from her went into him as well. The skirn sickness is altering Zedd's magic.