Multisite domain name is resolving really slowly

Hi,

Just wondering if I could please get some assistance with our domain mapping plugin. Of recent the domains that are mapped are taking a long time to resolve - between 10-15 seconds. That is way too slow. Please see the below links:

http://theunicorn.farm/
http://perspectiveiq.com.au/
http://vimtonic.com/

Any help or advice would be greatly appreciated.

Regards

Andrew Yang