Sri, my guess it is related to broadleaf dock, or possibly related to common mullein. There are several species of dock, but none of them quite match up. If you don't get an answer here, I suggest sending a picture to Bill Curran PSU extension weed specialist. Or maybe contact your local extension crops agent, and ask that person to send a pic to Bill Curran. See if you can find out that way. If he doesn't know, at least he should be aware that it exists. note: I am presuming that the purple stems are found on unsprayed plants - not just on the sprayed ones? | 
what kind of weed is this
