It seems you are not using any non-linearities.
While lasagne ships the non-linearity with some layers, e.g. Conv2DLayer 3, you have to define it in PyTorch by yourself.
Also the default init function for Conv2DLayers in lasagne is for the weights lasagne.init.GlorotUniform and for the bias zeros.
Could you change the init functions to xavier_uniform 7, which is also known as Glorot_uniform.