Weird fish problem......(tropical not GF or KOI)

I have two half barrels, each with a types of platy. One has
sunburst, and the other has red wag.......I initially bought 12 of
each type with 10 females and 2 males in each group. Within 48 hours
all 4 male platys were dead..........water parameters are dead on and
the water is perfect.......I exchange the bodies that do not move for
4 more that are alive and appear to be healthy........Same thing, 4
more dead males..........All the females are fine.............I yet
again carry back 4 bodies and get 4 more, in exchange and also carry a
water sample, just to make sure my set is not crazy, but it really was
not a concern as all other fish are doing fine, its just the males
kicking the bucket.......Water checks out fine by stores tests......so
this time I add another male to each group so I now put in three males
with each halaf barrel of 10 females (A suggestion made for fun by the
LFS clerk that maybe 10 females were just to much for 2 males to
handle, yea right....) anyway..........the 6 males all died within 48
hours.........So again I carry them back....none of the males in the
stores tanks have ben dying or at least thats what they have told me,
but they now again exchange dead ones for live ones......but this time
I I elected to go with all females..........Been a week or more now
and not a dead body...I even have a large population of fry in both
half barrels.........So am I missing something here in regards to
these male platys? I and no one else in the local Chain pet stores or
LFS has a clue......and the LFS said they will replace them as long as
my water is good........or until we can figure out whats going
on.....I did not want to take any more chances with them, so I bought
2 platys from Petsmart, this past Sunday.......and yep they are both
dead....................

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