Net speed relatively slow on my device as compared to other iOS devices on the same wifi network

IiPhone 6

ios 8.3

64gb

since last few days AppStore was updating the apps again and again even after they were updated once. Since then the net is working very slow on my device as compared to the other iOS devices that are connected to the same wifi network. Also observed that my phone is hampering the speed even when I'm not using it. Unnecessary data usage is taking place. Please help me resolve this problem.