A Tension in Reformed Theology

There seems to be conflict between these two theses:

I.  Goodness of Creation Thesis:  God created everything in an original state of goodness; which seems to imply that there would be no vicious characters prior to the first sin.

And; 

II.  Viciousness Thesis:  If some agent’s character necessitates or determines them to sin in some situation x, then that agent has a vicious character.

And given that I’m a determinist, then I believe that the first creaturely sin was determined by prior factors. So what should I do?  As the two theses stand, I don’t presently see a route of escape.  I’d probably modify (I.)--creation can still count as good, in the grand scheme of things, even if it contains vicious agents.  

Leibniz: The true root of the fall is the inherent imperfection and weakness of created things, which is why sin belongs in the best possible series of events (discussed above). That is why it was right for sin to be permitted, despite the divine power and wisdom; indeed, it had to be permitted if these perfections were to be given their due.