502 Bad Gateway nginx/1.2.1

Hello,
since a couple of days I am getting this error message all over my website:
502 Bad Gateway nginx/1.2.1

The thing is that my server uses apache... I have tried solutions I have found in google: erasing cache files on navigator and pc. and doesn't work.
I have talked to my server administrators, and can't find where the problem comes from.
Last option was, thinking that the issue comes from the Theme + Plugins I am using in my website (in wordpress) which is Talents Them from Kayapati. But they say the issue is not related to them...
So I am lost, and I don't know what to do...
Is there someone here that can help me, please?

This is my website: www.conmuchoarte.net

Thanks!