Double trailing slash after domain

I have a wordpress multisite which I have recently undergone the big task of changing from sub folders to sub domains.

So far, everything seems to be in order, however I have noticed one anomaly and I'm wondering if you might have any insight. When I look in the source code of my site, it appears the URL's for resources have double trailing slashes, here is an example:

Do you know what might be causing this issue?