Sorry, I missed the part of two new guppies were added a week ago the first time I read your post. It can be a problem. There is the possibility that the new guppies came with parasites. It is why a quarantine tank is always recommended for any new fish.
My advices from the last post still stand. Do the partial water change a few times (no more than once a day, and watch the temperature of the new water, let it be equal or close to the aquarium water temperature)) to see if the problem fixes itself.
If the problem gets worse, or if you start to see white spots, please get back to me here before try something else. ☺
|