Take a look at the ingredient label on your trichlor pucks--almost all of the pucks available around here also contain copper, which can stain walls green.

If the coloration is from metals precipitating, that usually happens when chlorine and TA levels are high. Your TA level is not, but shocking with any type of chlorine--trichlor, bleach, or anything else--will help the metals drop out. I would let the Cl stay low--in the 3-5 ppm range--and see if that makes a difference. It will also inhibit any algae from growing until Pooldoc or one of the other metals gurus around here can see this to offer advice.