You can put a layer of hardware cloth 2ft, 3ft or 4ft around the perimeter of the fence to cover the gap. Also, aviary net over the top of their run will prevent escapes.
Welcome! Don't worry. You'll go years without accomplishing anything other than chicken stuff. :lol:
If some of your girls are starting to lay and you're still feeding Start and Grow, do remember to put out some oyster shells (free choice in a SEPARATE container) so the new layers have a...