1. Crystal has never created an atmosphere. She manipulated the air they had before going into space
2. Prah’d’gul never created an atmosphere of out nothing. The moon does indeed have an atmosphere with gases but it's very very very weak because of the low gravity. All the gases usually escape into space after a few hours. All Prah’d’gul did was manipulate the weak Atmosphere. Which shows how detailed and powerful his energy manipulation is.
3. I also don't think Storm "generated" weather on mars more like manipulated its weak atmosphere patterns and its weak magnetic field and boosting it to stronger levels. Which is a huge skill feat and power for Storm.