Adafruit Ultimate GPS Logger Shield and Co2Meter (K-Series) together???

Hi All, I have an important question for my project. I'm using Adafruit Ultimate GPS Logger Shield on Arduino and at the same time reading Temperature/Humidity sensor from also Adafruit. It works well. Now I'm trying to add Co2 Sensor ( that also use tx rx but in pins 13,12. But after trying for many hours I don't find the way to make them work together. The problem I have is that the SD card can't create the file. But looks like both systems are fighting for the Tx RX port to send the information. How can I mix this two sensors??? (GPS and Co2)

Thanks a lot for the help


Which Arduino do you have? Which shields do you have? Post your code.