Paracyprichromis deaths

I've lost a couple of Paracyprichromis nigripinnis out of my juvenial
school (was 9, now 6) in the past couple of months and am wondering if it
is possible that they were harassed to death. They are housed in a 40gal
with 3 juvenial calvus and 1 adult male similis. The similis was put in
that tank after he was kicked out of the colony in the similis tank. He is
constantly chasing the paracyps, particularly at feeding time. One of the
paracyps that died had congentital abnormalities (almost looked like a
different species compared to the others, dark chocolate brown color,
large eyes, slight curve to the body behind the head), so I chalked its
death up to that. The others that have died haven't shown many symptoms
other than hiding in the java fern on the opposite end of the tank from
the similis, occasionally clamped fins while hiding and a slightly
darkened coloration. The bodies show no signs of spots or discolorations,
but the one that died this morning had several gill rakers pulled out from
under the gill plates and the tail was frayed, but that may have occured
after death.

Of the living fish, one had a torn tail, but is still out cruising the
tank with the school and another is hiding in the java fern. Water
parameters are fine (0 ammonia/nitrite, 10ppm nitrate, pH 8.4, KH 20ppm,
GH 15ppm), but it has also been rather warm recently (spring "heat" wave)
so the tank water has been about 85F during the day for several days. I
also had a little incident with the filter last week that caused about 10%
of the tank water to end up on my floor, so they got an unexpected "water
change" then. The calvus and similis show no signs of disease, although 2
of the calvus also spend a lot of time hiding out in the java fern. It has
also been the smaller paracyps which have died and they've not been
growing as well as the rest, so perhaps this is some sort of failure to
thrive issue.

So does this sound like a disease that the paracyps are more prone to,
stress, failure to thrive or something else? I am planning to move the
similis (assuming I can catch him) to my 10gal isolation/hospital tank
once I move the cardinal tetras which are currently in there (recovering
from being battered) to my betta tank (and hoping they don't get battered
by the old betta there).