Thank you. The reading you got was for pH, and that is ok, and though a bit low shouldn't cause problems. What we really need are readings for ammonia and nitrites. Both of those chemicals need to be at zero. It's best to use a test kit that has test tubes and chemicals you add to water samples. Testing for ammonia and nitrites with strips is unreliable. Water quality can affect many different health conditions.
The white spots are most likely carp pox. Carp pox is caused by a virus in the herpesvirus family. It causes white or pink waxy bumps in various sizes. Some will disappear. New ones may show up. There is no cure for it, but the affected fish seem to live healthy normal lives with it. It is believed that most goldfish have been exposed to it, but have built up a resistance to it so they don't become infected. If they are stressed, an outbreak can occur. You can read more about it here:http://www.ponddoc.com/koihospital/Diagnostic/Other/CarpPox.htm
As you suspect, the most common cause of a fish being unable to close its mouth is something caught in the mouth or throat. It could be a rock, a piece of stick that has fallen into the pond, or any of a number of foreign objects. Often, a fish will finally manage to get the object out, and many pond keepers do nothing. If you want to try to help, you'd need to catch the fish. Wrap it in a wet cloth, and hold it head down. Rub the throat in one direction - toward the mouth- to see if that will dislodge the object. If that doesn't work, you can open the fish's mouth, and using round-ended tweezers very gently take hold of the object and dislodge it. You do need to be very gentle throughout this process. Sometimes the cause isn't an object, but rather a sore or tumor in the mouth or throat. In that case, the only solution si to have an aquatic vet treat the fish.
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