WordPress Admin panel slow after migration to faster server.

Hi all, bit of a head scratcher for you.

I’ve recently moved a client website from a VPS hosted with LCN that had 2Gb RAM and about 8Mb/s upspeed, to an in-house server, i7 and 8Gb RAM, 12Mb/s upspeed. Both servers run Plesk.

On the in-house server, the admin panel is much slower. The site hasn’t changed at all, it’s an identical copy. On LCN the admin panel pages load instantly and on the in-house server they take about 4.5 seconds.

This isn’t a major issue for me but the client is concerned that it’s a lot slower and slowing down his editing of the site which is understandable.

I’ve upped the PHP memory limit from 64Mb to 512Mb and no difference, I have been considering trying to deactivate plugins, however the only active ones are necessary for the function of the website and they don’t cause the admin panel to run slowly on the LCN server.

I can’t figure out where the difference is that makes one slower than the other. Every other website we’ve transferred is noticeably quicker off our in-house server.

Thanks to anyone that can help!