Continuity mistake: While Clark is chained up, Chloe uses her fingernails to dig into Clark's chest. You can see that since Clark has had his powers taken away her fingernails draw blood. In the shot of Clark screaming in pain you should see where the blood came from the scratches but there is no blood visible.
Audio problem: In the scene where Jason and Isabelle/Lana are talking and he is about to burn the book with the lighter, she quickly grabs the book with her magic. Isabelle then says some sort of spell flinging Jason against the wall to the right. In the shot where you see him thrown against the wall, Isabelle has already said the spell, but you can see her mouth moving saying the same thing (though nothing is heard).