I would already say that your cloud and your sky is not clear. Enlarge to more than 100% you will see it yourself. Then the exposure of the buildings on the shore would have deserved to be a little more overexposed. You can easily solve this problem by using localized masks on LR, brushes or radial for example. The sky also the whites are burned and the gray of the sky can be improved. I understand your approach, but as a general rule it is better to give color images and let the customers themselves pass them in black and white. On the other hand, color or black and white, it is important to work on what I wrote to you above. Watch out for the noises!
Short answer: Do not submit B&W photos.
Customers want full color. If they need B&W, they can do that themselves in Photoshop.
Read the DO's & DON'Ts in your Stock Contributor User Guide.
Quality & Technical Issues:
Monochrome, underexposed, not sharp and white halos along the edges of the subjects.