Don't forget that, every time there is a storm, the waters get churned up and cooling of SSTs takes place. It's even possible that Erin will help prevent Dean from becoming a truly huge monster.

The time differential is more than 8 days and TS ERIN isn't consuming that much yet. (The stronger they are the more heat they consume)

So, in this case, I don't think they will affect each other in that way.

The loop current in the center of the gulf is nearly impervious to churn, hence katrina, rita, and many other storms' massive power run-ups as they crossed over it. This effect made them rewrite the models. Normally, a slow hurricane is dampened by its own churn, except in that area where the water is hot, deep.