With Mu and Jade, I've found it easier, since they seem to have a weird provocation of each other going on there. Actually, it's something of a delight for me, because I've never seen quite this side of Mu.

One problem I've had with Isaac is that sometimes, there doesn't seem much to go off of in a response to him. And I suspect this may in part be because you're feeling shaky, so it's hard to get a response out of it. Have you considered trying to push through that and just give longer tags? Elaborate more, let the muses blurt out more? I know that sometimes when I'm having trouble with one, forcing them to actually speak more than I might want to kicks the voice and personality back into gear.