Dear @JF
there is not really a LayTheme solution for this. This is an Wordpress issue I assume.
https://www.google.com/search?rlz=1C5CHFA_enDE828DE828&ei=RZeGXOOsLeKOrwSh6L-4Aw&q=wordpress+mailto+in+navigation+opens+blank+page&oq=wordpress+mailto+in+navigation+opens+blank+page&gs_l=psy-ab.3..0i71l7.8042.9264..9490...0.0..0.309.2650.2-8j1......0....1..gws-wiz.cgzOJY84lJ4
Dear @kfairhurst
did you use CUSTOM CSS to change them?
You could - to override the settings. Then be aware of the CUSTOM MOBILE CSS which is only for mobile.