Oh no! You finally get the piece to work and it does that. :( It sounds like you are dealing with crocking. That is when a fabric is bent and the color literally rubs off. It usually happens when fabrics get to wadded up in the dryer but can happen outside the dryer, just not as often. We don't see this much anymore due to the way fabrics are dyed today but it does still happen occasionally. Red, green, and yellow fabrics seem to be the worst for this and it can happen even if you prewashed your fabric. I'd say since your fabric is yellow-green and a batik you probably just got the one fabric out of a thousand that this would happen with. I'd call that block a practice block and if it isn't too bad, use it on the back somewhere or as a label, or save it to practice your quilting on. Good luck!
~Tiffany