I tried to attach a picture but from what I can see that hasn't worked. Hopefully you will be able to see the picture with this link https://ibb.co/m9DO1o -- it goes to a free file sharing site.

I would propose that you use antibiotics to treat the spots. You should also try to change water in the pond.

Usually a common cause for fish diseases is hygiene. So we just have to inspect the quality of our fish tanks/aquarium and replace it with cleaner water. In my case, I change water twice a week since it doesn't have any filter. If it'sabout something else then we can use tabs appropriate for the fish disease.

Try to change the water more often, how many fish you have in your fish tank maybe your tank is overpopulated if this not your problem than I think you should do 25-30% partial water changes every other day.

If it's been their for too long but no bad things happen to your fish then I think it's not that serious. But you can try to consult professionals for them to diagnose your pet just to make sure that it is really okay.

I agree that the common cause of fish diseases is poor hygiene. Owners must always check the condition of their aquarium or tanks. The life of the fish depends on its temporary habitat, which is your aquarium, we must take responsibility as an owner to keep them clean and also maintain a proper feeding schedule. Fish cannot live without food that's a common thing for all living things so as a pet owner we must be responsible in feeding them on time. If we take good care of our pet fishes, then their life span will be longer.