I visited the Azure link that you provided and the icons appear correctly in contrast to the screenshot that you shared.
I assume visual difference is due to the fact that some the sprite
image is not loaded for some reason. Check the network tab of your browser, reload the page and search for any failed requests. Or maybe the bundling and minification is failing, if you use binding and minification try to add the files separately (without using bundles) and see if it makes a difference.
Let us know your findings.
Check if the path to the sprites is also correct:
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