Hello and welcome to Binky Bunny. Even though your bunnies are sisters, you are going to have to separate them soon. When rabbits begin puberty, which can happen as early as 12 weeks, they can become aggressive and territorial. This can lead to fighting and severe injuries. Their gender doesn’t matter, not does the fact that they are littermates. They will need to be separated until they have been spayed, and at least a month has elapsed since their surgeries. Then you can go through a proper bonding procedure. They are not really bonded now, that can only happen after spays and neuters and bonding sessions. They get along fine now because they are so young and not dealing with hormones yet. But that can change very quickly.
Here are two good articles on bonding:
http://rabbit.org/faq-bonding-multiple-rabbits/
https://binkybunny.com/BUNNYINFO/tabid/53/CategoryID/9/PID/940/Default.aspx
It’s advised not to start giving any veggies or fruits until a rabbit is 12 weeks old. Then you start slowly, with one veggie at a time, trying a new one every few days. Otherwise, you can have stomach upsets. Fruit should be given very sparingly. The same with carrots. They have a lot of sugar and that can cause gas or other GI problems.
Rabbits are curious, so it’s natural that your one rabbits likes to sniff the same things every day. There could be new scents on them from day to day anyway. No two rabbits are alike. Some are more people oriented. Some are more active and some are more laid back.