fullcalendar full vertical borders

my fullcalendar collided with my bootstrap css file, so i must set my style manually. (I use fullcalendar 2.7.3)

I want to have red borders (horizontal and vertical). I changed:

.fc-row .fc-content-skeleton td,
.fc-row .fc-helper-skeleton td{...}

and that created me horizontal and vertical borders. But the vertical borders only showed in the head of the cell. (Screenshot) How can i insert a full vertical border.