Nice scene. Agree that the horizon has been dissceted into two halves. Slight crop from the bottom to remove the dark band with no details would strengthen the image. Alternately, you can also crop a bit from the top.

In competitions like BBC, minor cleaning work like dust spot removal is allowed. The reasoning is the dust spot is there in the sensor and not part of the scene you are recording. Cloning to remove dust spots is ok.

Cheers,
Sabyasachi