Finally got a DSLR! (T4i)
Congratulations...enjoy your new camera and lenses.
Try stopping down the lens. I'll use F16 with the 55-250mm lens often. When we are close to the subject shooting wide open at full focal length the depth of field is extremely narrow. Check some depth of field chart on the internet...you might be surprised how narrow it is. Don't worry about noise or lens diffraction or anything anyone tells you that stops you from experimenting...push the limits...learn from what you see and experience.
this helped me a bit. here is a pic I snapped using your advice to stop down the lens.