20% is a bit much for an every week cleaning, and the 40% is also. Changing too much of the water at once can lead to issues with the beneficial bacteria, and that can lead to stressed fish (and sick fish). Are your water parameters ok? If so, she's probably fine...she shouldn't be sick if her environment is healthy.

Happy Halloween.
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Phishie
Site Coordinator

"An ounce of prevention is worth a pound of cure."