A better idea would be for the OP to give us some idea of what he means by "trouble". Without knowing what the actual problem is, making any suggestions is going to be a waste of time.
More information would help. But I will confidently bet my money on the trouble being "my pictures are blurry" and/or dark.
... and didn't upgrade your lens inventory? Although the 70D will be better in most cases compared to a Rebel T3i, it is the lens. It is always the lens.
EB EOS 1DX and 1D Mk IV and less lenses then before!
