You didn't use just 3 ppm of chlorine or you wouldn't have dented the volume of algae you say there was in the resin bed; you used much more than that and then let the resin sit in it for an hour.
And you are here now asking if you should replace your resin because of what and how you did it.... yet now saying chlorine can't be that bad for resin. That depends on the amount of chlorine in the water.
In 20+ years of selling and servicing softeners I've never heard of or seen algae down in the resin, algae needs sunlight to live/grow and although the right color tank allows some light to get trough the tank wall, resin does not allow light through it. BTW, I've dealt with a number of softeners etc. that are installed outside in direct sunlight. Usually only natural non-colored tanks allow a greening on the inside of the tank above the resin in the tank and usually only on the underside of the tank's dome.