For every new reptile you get it is a very good thing to quarantine the new animal for at least 2 months or more. You dont know what your new reptile may or may not have, and introducing them like this means that anything your new reptile has, your old one now probably has too. When you get a new one, make sure to wash your hands directly after you hold/touch it, before you touch anything else. Make sure to take it in to a vet to have a check up and fecal exam done. This will allow you to be sure that you arent introducing new parasites or other potential health problems to your other lizard. Then wait the couple months or more so that any problems have a chance to show themselves before they are passed to the older lizard.
As for extra care, yes females will usually cycle eggs when they are older, so a much higher amount of calcium and other minerals are needed. Regardless of sex, at that age, ALL live food should be dusted with a calcium powder each feeding, gut loaded with the same veggies you feed your dragon, and dusted with a vitamin/mineral supplement twice a week. For your male, you still need to be dusting and gut loading his live food. It should not be necessary to ever dust vegetables as long as you are feeding a good variety of appropriately nutritious ones.