My sleepy goldfish

Question
Hi Michael,
I am new to keeping goldfish. I just got 2 baby goldfish few days a go, 2 days after I got them I went and got filter+air stone for the tank. While I put on the equipment, I scooped the 2 fish using cup and put them in another. An hour later, I pour them back into the tank with 75% of fresh water. They were very happy initially after I put them back, however, one of them, has been "sinking"at the bottom, looking very lazy and motionless since then, and until now, which has been about a day or more. She will once a while swim quite crazily, like a 'crazy man' for a very short distance, and then go back to her motionless state. The very first few days I got them, she wasn't as active as the other one, but she was definitely moving around, unlike now. Whereas the other one, he has been moving around since I had them.
I wonder what's wrong with her, will she die very soon?
Thanks for your help.

Answer
May,
the 75% water change may have caused the eratic behaviour.
about all that you can do is to watch them for signs of stress.
If you have awater conditioner it would not hurt to add some in, like stress coat.
don;t change that much water unless you are in an emergency situation.
if you have other questions, just ask