Calor Poison

Have not tried 4b, this occured in 4a ... Had eliminated Calor system prior to msg event about these same folks poisoning one of my planets. Found ship of calor hanging around and destroyed same after event .. is there supposed to be a return to normal on posined planet if so didn't occur after 20 turns of play. Possible if destroy system before msg can not clear up (unless not implemented yet). Just wondering .. anyway on to 4b.