You have to revise and reorder your code structure.
Your site loads 27 render-blocking javascript files and 33 CSS files before the content above the fold. Also you load some plugin content before the styles are applied.
Try to defer the blocking CSS and JS. Load everything early that is needed to display the first visible content (=above the fold) and load anything else after this.
In your case you could try to locate jquery, navigation and the form plugin scripts in the <head> and locate the sliders scripts in the footer. If there are no problems locate jquery and dependent scripts in the footer using wp_enqueue_scripts. Generally load CSS in the <head> and JS before </body>.
This review and this waterfall chart are showing the loading sequences of your site. Take a look in the details on how to solve the several issues.
Additionally you should:
- Declare a doctype in the document head
- Use a caching Plugin such as Autoptimize or W3TC
I guess your problems result from wrong load order.
You can use these tools to analyze your site:
- http://www.webpagetest.org/
- https://developers.google.com/speed/pagespeed/insights/
- http://tools.pingdom.com/fpt/
- https://gtmetrix.com/
They do basically the same with little differences in reviews.