textbox height – CSS

Hi,
I’m testing this plugin (http://wpdevart.com/wordpress-booking-calendar-plugin/) and it’s wonderful, but I’m having a problem with textbox height in the forms.

Accessing to reservations from the plugin options, the size of the textboxes is ok, but when I put the form in a page, their height is about half-sized and I can’t see the letter when typing.

Is it possible to be a conflict with Graphene Theme CSS? Where can I see the textbox css of the plugin to check it?

Thanks,
Miquel

https://ww.wp.xz.cn/plugins/booking-calendar/