I have had the issue. A while back (early summer) my husband ordered some 100%VG nic from them. I didn't get around to trying to use it until the 30-day period had expired, so I didn't bother contacting them. Even so, it was HORRIBLE. Utterly unvapeable. Even diluting it down to 5mg nic it was incredibly harsh and nasty. I cannot express how horrible this stuff was. I threw it out.
From what I read in a thread on their forum here, at one point one of the labs that was making their nic was adding something to prevent discoloration and SOME people but by no means all, were sensitive to this ingredient. (I'm obviously one of those people.) Those who contacted RTS about it received a refund. Subsequent batches, according to the thread, have been made WITHOUT that ingredient. So if the problem existed at some point, it likely no longer exists in newer batches.
I have not tried any RTS nic since and have used the stuff from Blue Mist instead, though I'm sure it is fine at this point. I did recently get an order from RTS just to test, but I haven't gotten around to it.
What I suspect is your nic came from one of those bad batches. I would contact RTS, and explain the problem. I'm sure they'll issue either a refund or replacement as needed. Other than some drama thing, I haven't seen anyone say anything bad about RTS service and it appears they issue refunds without question in the 30 day period.