static & https vhosts with Apache reverse proxy problems

Question

I have a running site with an Apache Reverse Proxy frontend of my webserver ddbb backend. I have 3 vhosts:

1. www.mydomain.com -> reverse proxy to webserver ddbb
2. static.mydomain.com -> css, images & js file hosting
3. secure.mydomain.com -> reverse proxy to webserver ddbb, but HTTPS with mod_sll

I wish a separate browsing, standard http all time, except when you visit "my account". The systems redirects to secure login https://secure.mydomain.com.

It works very well, but Chrome warns me about my site is still linking non secure static content http

I tried to add "static" alias under secure.mydomain.com vhost but it does not work. I think the problem is that my secure vhost secure.mydomain.com can't host files, as it works as reverse proxy...

How would you solve this? Maybe a 4th secure vhost? or all site browsing under https must use a lot of CPU isn't?

Please your recommendations would be very appreciated! Thanks in advance.