Does anyone have problems with the Stucco theme not rendering Google fonts correctly on Ipads and Iphones?

I am building a C5 Stucco site and have copied and amended one of the presets (both the .less files that are used, in the css/build/fonts folder and in the presets folder), named them appropriately and the Preset shows up with that name in the customise window, can be selected and works fine on a desktop in Chrome and Opera. Both the Google fonts I've chosen appear as they should on a desktop.

However they don't get called at all on an ipad or an iphone and I just can't work out why. I have even tried renaming my two .less files as "defaults.less" so that they get called by main.less come-what-may (as was suggested on another thread), but still the fonts are not used on my mobile devices. Can anyone tell me if there are further files within the theme that override the presets and if so where they should be changed please?

I'm running Stucco 2.1.3 on C5 8.2.1 and most other things seem to work fine !

Any and all advice gratefully received