DelfinT wrote,
Today I found out my favorite fish "Jackie" ( I would like to think
she is a girl) has hole in the head.
She has not lost her appetite & is behaving normally except for
sometimes trying to scratch herself on the driftwood....

If that is the only symptom - what makes you so sure it's hole in the
head disease? I suspect your seeing pin-sized holes near nostrils, gill
plates, or near eyes and/or thin white threads trailing from the pitted
depigmention lateral line.

I read somewhere on the net that earthworms fed to the fish by itself
will cure it without a need to use medication.....

One suspected cause for hole-in-the-head is high organic levels - poor
water quality! ... Not just any earthworm, red earthworms have better
nutrition and more vitamin "D". But, like 'maria' pointed out,
hole-in-the-head is most likely due to Hexamita, not just a mineral
and/or vitamin "D" imbalance. Easy treated with Tetra's medicated food
called Metronidazole, if you can find it. If not, you may be able to
find Metronidazole in the store as Hex-A-mit. 250mg capsules - 1 cap
emptyed into 10 gals. every other day for 5 days. I would also open 1
cap. and mix it in a tablespoon of shrimp or fish oil, then mix it into
20z. of a good flake food or 1/4 pound of frozen brine shrimp and feed
it twice a day for 10 days - works better than to just dump it into the
tank...

then go back to my maintenance schedule
of a 50% water change every other week...

A 20% weekly water change leaves about 30 days of accumulated DOC
(dissolved organic compounds) pollutants in the tank. You can get away
with less water changes with the other fish you listed, but discus need
much cleaner water. When I was really into the breeding, my discus
breeder tank got an 80% water change every day, otherwise they wouldn't
breed! I'm not saying you need to go that far, but I do think you need
to be doing at least 4 or mabe 5, 20% weekly water changes, just to
keep the DOC level down. A lot more live plants would also help, as
would bio-wheel filtering............... Frank