The big one is a sulcata tortoise and the small one is a leopard tortoise. They should not be living together or having any contact.
Here is some care info:
http://www.tortoiseforum.org/threads/how-to-raise-a-healthy-sulcata-or-leopard-version-2-0.78361/
http://www.tortoiseforum.org/threads/beginner-mistakes.45180/
http://www.tortoiseforum.org/threads/for-those-who-have-a-young-sulcata.76744/