Can using NPOT sprites be the reason for performance loss on older phones?

I'm testing my game on phones like(HTC Desire X & similar) and there seems to be a loss in the performance in comparison to newer phones. I did some research on POT & NPOT textures and they say that on newer phones the problem would not be big at all. On the oldest phones this is impossible and thee middle class, it's possible but they get laggy while working with NPOTs.

Above you see one of my biggest textures. What does your experience say, is this too big for NPOT textures, taking into consideration that I'm targeting android phones os 4.1+? Should I convert my textures to POT, or I should first check for some other problems with the code or other stuff causing performance problems?