Other way around; that's probably a N overdose. Other possibilities to show that leaf shape are not enough ventilation or too little useable root space for the size of the plant (this includes if you are overwatering your soil into a mucky mess at the bottom fo the pot).
Fill out the troubelshooting form for more help, but next few waterings, give jsut water, and make sure your soil is drying out pretty well in between.