Girlie, I don't think that is too soon to cause a herx. It sounds like it could be Bart. So, don't panic yet! Bart rashes can pop up at any time. Since we can't rule out an allergic reaction, maybe you should check with your LLMD. I think it is more likely Bart. Bart can cause red blotches. I'm not sure what your rash looks like.
I have been herxing with GSE. Herxing happens pretty quickly after I take them. Today, I was thinking how my skin has been doing much better. Then, BAM, I have a brand new red dot rash out of nowhere. It looks like a little patch of Rocky Mountain Spotted Fever! But, it most likely is not. These bugs just need to die, die die.
I think chances are your rash could be Bart. Lyme can cause some weird skin symptoms too. Anyway, here is a thread that may help:
http://www.mdjunction.com/forums/lyme-disease-support-forums/general-support/11076158-check-out-this-rashbart-or-rifampin
On a side note, did you take Psy-Stabil? If so, did it help you? I'm considering trying it based on my LL's recommendations.