Another day and another blow to Microsoft's struggling platform. This afternoon, popular photography site 500px sent out an email to members announcing that they were discontinuing support for their Windows Phone and Windows 8.1 apps at the end of April (Chrome OS was also listed).

Indeed, the 500px Windows 8.1 app is already unavailable, although the Windows Phone one – last updated in January – is still listed.

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The email, entitled 'Reevaluating our 500px Apps', explained the reasoning behind the move:

"As the 500px community grows, we're faced with the ongoing challenge of reevaluating our product lineup. This ensures our team can focus on the products that will enable and reward visual creativity for the most people at the highest standards of quality."

"With that in mind, I'm writing to share that our Windows Phone, Windows 8 and Google Chrome OS applications will be discontinued at the end of April. Members using these devices are encouraged to use our website at"

Luckily for users, there are plenty of well-reviewed third-party 500px apps to use on both platforms. Nonetheless, it is yet another chink in Microsoft's armor and more bad press as they head into next week's Build developers event in San Francisco.

Thanks, René G, and others for the tips!