Problems keeping Gold Rams alive

Initially I bought 3 Gold Rams and put them in the main tank. Within 4 hours
2 of them had died. There was a very slight trace of ammonia (and I'm
talking hardly off the scale) so I moved the remaining Gold Ram to my son's
tank where it was very happy.

Once the ammonia settled down and all readings were 0 apart from the PH
which was between 7.0 and 7.5 I bought another Gold Ram for the main tank.
Again he was very happy.

My son then wanted a Betta for his tank which we bought. The Gold Ram in
that tank bullied the Betta so we moved him into the main tank downstairs.
Within a few days he started to be unwell....I tested the water and all was
fine and moved him to the "hospital" where I treated him for the "Pop-eye"
he had developed. Unfortunately it was too late. About 2 weeks later the
second Gold Ram went downhill very rapidly and before I had a chance to move
him (power cut coinciding with me spotting this) he had died.

So what I have, is two seemingly healthy Rams that cannot cope with life in
the main tank. Firstly I suspected the PH but my LFS who sold me the fish
has the same PH and they have been allowed plenty time to adapt to this.
Additionally, they seemed to cope when they were on their own - one in the
main tank and one in my son's tank.

Now, my son wants to set up his "new tank" - he has MTS (just like me). But
he wants to be able to prove he can keep Gold Ram so I need some hints to
help him achieve this. Part of my theory is this might relate to stress and
bullying going on elsewhere in the main tank but I need to be sure it might
not be anything else.

The main tank has the following inhabitants/history

4 Blue 3 Spot Gouramis - at the time of the initial introduction there where
2 males and 1 female. Another 2 females were introduced. Just prior to the
demise of the first Gold Ram the non-dominant male was killed by the
Dominant male

6 Platys - breeeding quite happily as platy's do :-)

6 Clown Loaches - the two largest starting to fight it out (in a friendly
way of course) for dominant fish. All resolved before the second Ram died.

5 Fantail Guppies - all male but not very aggressive

A number of Neon Tetras - was 11 but hard to count how many are in there
right now

1 fry - presumed to be Platy

The tank is 47.5 UK gall so enough space I believe....

I do not want to put any more Rams into this tank, as much as I love them.
But I would be interested to hear if anyone has any theories as to what went
wrong especially if my son is going to attempt to keep them? Could it be
down to stress in the tank which is the only theory any of us can come up
with?

I would welcome your opinions as I really like these fish and would love
either me or my son to be able to keep them successfully.

Thanks
Gill