Mollies Mysteriously Falling Ill

[cib]

I have a 60L tank - simple ... tank, fluval filter, heater, pebbles, 3 shells - been going for 5 weeks.
Cycled for 10 days, added 6 neon tetras (Bought at local garden centre), all seemed fine.
Left it for 8 days before I bought 5 Sailfin mollies (bought from Pet's at home) 1 1/2 weeks ago.
Also added that day an aerator and two plastic plants.
On the day of buying, one died (could only diagnose it as stress).
Following day, another followed suit.

I had the water tested but other than a slightly 'uncomfortable' water quality associated to a new set-up, all was fine.
I have delayed adjusting anything in the tank to allow it to settle with the exception of building the bacteria in the tank with 'Nutrafin - cycle'.

I have done weekly water changes (approx 10-15%), used 'Easybalance' and used the Nutrafin - Cycle as per the instructions.

Today, I noticed white-spot on one of my Mollies (the male) so bought some medicine. Added it as per instructions on bottle.
2-3 hours later, I spot the Male Molly virtually dead ... upside down, gasping ... almost gone. It died within 10 minutes.

Does anyone have any idea what might have happened ?
The only thing I can think of is the medication for the White Spot but the other fish appear fine.

Last week, one of the mollies gave birth to a few babies (I have them in the same tank in a nursing enclosure (3 survived)) and they are thriving in the tank.

If there is something wrong with the water, the other fish show no ill signs and the babies have survived this mystery problem.

I'm completely stumped and until I can solve it, I'm very reluctant to continue keeping fish - I don't want any others to suffer.

Please help !

 

[WILDER]

Whitespot can be a fast killer if it affects the gills.
You should only be half dosing with fry.
Have you increased aeration in the tank with the high temp and med.
Have you raised temp to 30.

 

[cib]

Whitespot can be a fast killer if it affects the gills.
You should only be half dosing with fry.
Have you increased aeration in the tank with the high temp and med.
Have you raised temp to 30.

I did raise the temp a little bit (to 83/84 F) and the aerator is now flowing at max rate ... just basic steps i took when i first discovered the white spot.
I couldn't see anyhting around the gills but the male did have quite a lot on his tail.

There has been yet another casualty. Only one of the original 5 remaining.
On the up side (although i thought this of the last golden molly), the other silver molly appears to be fine as are her frys.
The neon tetras appear to be unfazed by anything that's going on !

Thanks for your help but this appears to be a mystery ... i'm still lost as to why they are ill let alone dying.

 

[WILDER]

Whitespot can be fetched on by stress, and temp dropping to fast,

 

[cib]

Whitespot can be fetched on by stress, and temp dropping to fast,

There has been no drop in temp - I was planning on slowly reducing it today back to it's original temp.
As to White Spot ... the other fish (for now) don't appear to have any white spot but I'm adding treatment to make sure.