(To go back, click the right mouse button, click on "back")

The first thing to check is water parameters.  Fin rot is complex, like most problems.
1. Ammonia or nitrite spikes (due to electricity off for a while, impeller jammed, water flow slows, somebody overfed the fish, etc.) Usually, redness will appear in the fins.
2. Chronic high nitrates, high pH.
3. Salt creep.  High salt will trash fins.  For those that use softened  water, the sodium level can be very, very high without you being aware of it.  Saltiness is a function of chloride ions, not sodium.
4. Parasites. The slime coat is not easily breached, mostly it is parasites that do this.  Both bad water and parasites will increase the thickness of the slime coat.  The fish will look "cloudy" or not as shiny as usual.  If there are no other symptoms, a salt dip to strip off the slime coat and remove most of the parasites, followed by a mild (0.1% salt) in the water to stimulate slime production (which will contain antibodies) is the least toxic route.  Continued dipping of tail fins in salt will often stop the parasites while giving the fish time to develop immunity.  Moving the fish bucket to bucket to leave the parasites behind works well.
5. Bacteria.  They invade when the parasites have trashed the slime coat. Treating as above and feeding antibiotic food puts antibiotics into the tissue of the fish.  Feeding antibiotics is the best, safest and least toxic treatment.  The exception is external columnaris and staph (of the hood or wen).  Columnaris is treated with potassium permanganate, feeding antibiotics prevents internal infection.  Staph is treated with peroxide and antibiotic creme.
6. The rotating bucket treatment is choice when the cause is not obvious or the fish has already been treated and it didn't work.

Often, fish that aren't eliminating don't feel like eating. However, the first thing to try is feeding some minced cocktail shrimp.  If they won't eat that, then they are off their food.  If they have been pooping, look over the diagnosis according to poop and the fish physical. A mushy belly indicates an internal infection.  If there is nothing specific, start with changing the water and seeing if their appetite picks up.  If this doesn't bring them around in 24 hours, then a salt dip is used to purge them out. Fancy goldfish should not be allowed to go without eating for more than 5 days.  AFter that they need to be force fed.  Start with strained peas (baby food) in a small syringe.  Get the tip of the syringe (NO NEEDLE) all the way into the back of their mouth past the gills.  A fish will open their mouth as they are brought to the top of the water.

The most common cause of this is high ammonia or nitrites. Check water parameters.  Next check fish according to those outlined for lethargy.

First thing is to check the gills.  It is possible the eating air is an attempt to clear the gills.
Goldfish do not have an opening from the intestines to the air bladder like other fish. Air enters and leaves the air bladder by a "rete" or net of air exchange capillaries in contact with the air bladder.  Systemic infections can cause scarring of the tissue where the exchange takes place, or it can cause adhesions of the air bladder to other structures that prevent correct functioning.
They do seem to have the urge to swallow air in an attempt to relieve air bladder problems or indigestion.  Some air eating fish that have been autopsied have shown systemic columnaris infection and adhesions around the air bladder.  Fancy goldfish are particularly susceptible.

1. Intestinal worms
2. Toxic water, do water changes.
3. Females that are spawning will do this when they are tired.  Head standing stops the males from driving them. Ryukins will also "tail stand" when worn out.
4. Frontal kidney damage
5. Gas from bacterial action on food

1. Spawning exhaustion, fish will have sorta soft belly (see physical) and anal port will be an "outie".
2. Toxic water, check the gills (see physical).

The first thing to check is if the light is coming from the side or overhead.  Fish align themselves to the light source.
Second would toxic conditions in the water, or toxic medications.
Blind fish cannot orient to light.
Infections, bacterial,  parasites, peritonitis and viruses can so weaken a fish they cannot stay upright.
Sometimes fish on their side do not have enough oxygen.

Fish yawn in an attempt to clear their gills.  If this occurs more than a few times, it indicates problems with the gills.
They open their mouths in an "O" when they have a rock
Fish also yawn when exposed to toxic compounds in the water, like hydrogen sulfide.
Yawning occurs when gills are infected with parasites or bacteria.

This is most likely dead brain flukes.

Fish may act like they are blind at times. They will also hide or stay on the bottom until feeding time.  They may list to the side.  There are three main reasons for actual blindness:
1. Losing eyes.  "Bug eyed" fish lose them by bumping forcefully into something.  This can also happen during spawning.  More insidious is the eye eating fish. Fish find food by smell, not sight.  All fancy goldfish need sinking food in any case, but blind fish do not need a lot of competition for the food.
2. In Orandas and Lionheads, head growth can grow over the eyes, restricting sight.  Again, feed sinking food and keep them with slower fish. Head growth CANNOT be trimmed except by an expert.
3. Brain flukes can cause blindness.

Fish with wens or head growth grows in spurts and in uneven spurts on various parts of the head.  When it does, "stuff" like even food or poop can get caught in the crevices and a little "fungus" might work on it.  They also get "pimples".  As long as the fish is bright, perky, bopping along and eating fine, leave them alone, don't add stuff to the tank. If it bothers you, the best thing is to take a Q-tip soaked in peroxide and rub it a little, but DO NOT get any peroxide in the eyes or gills.  Even a water wetted Q-tip might dislodge "crud" caught in the head growth. The dark blotch is a healing area, this also happens with head growth spurts.
However, if the spot is a dark red and it appears the wen is collapsing, this is a Staph bacterial infection and needs to be treated aggressively with peroxide on a Q-tip at least twice a day.  Move the fish bucket to bucket to get them away from bacteria.  Feed antibiotic food.