I bought 3 baby bettas this weekend at Petco. Two are very healthy and active but one seems to be missing its tail. She eats but can't really swim good. She still has her little side fins and can wiggle herself up for air but she has to return to the "sitting" position afterwards. She can't stay afloat like other fish. She was like this when I got her and I honestly didn't think she had a problem at the time. All the babies seemed scared and were laying in their cups. Now I'm worried she is sick or deformed. Do tails grow back? Is this fin rot? I currently have her in a very small habitat so that she doesn't have to go too far to get to the top. I do have plants in there though and a hammock in case she would like to lay near the top. I'm also monitoring the heat. I honestly just don't know what to do for her at this point. Even if she is sick I would like to make her comfortable.