the situation has gotten far worse.
Today one of my dalmation mollies died out of the blue, (swimming around fine, 2 hours later dead), the platy still shows the same symptoms however he has got slightly better and seems to swim around occasionally but slightly lethargically and also takes some peices of food. Only problem is has become very thin.
Unfortunatley i havent been able to get to the lfs today and i definately wont be able to tomoro (uni open day in portsmouth, starting marine biology degree this sept although after this they might not let me!!), hopefully my test kit will arrive tomoro.
I will fully inform you of the sequence of events

04/02/2007 Bought tank and let run for 1week and a day using "nutrafin cycle"
12/02/2007 Bought first fish- 3 z.danio 1 female platy
about 4/5 days later 2 z.danio died (i believe after spawning, hence i now have 8 fry)
about a 2 weeks later bought 2 mollies and 1 male platy (not with breeding in mind just random selection)
today mollie dies male platy in bad way
i think the tank must have started/continuing a cycle when i put new fish in (looking back a bad idea) and now must of hit a spike of some sort,
what should i do, all other fish in the tank seem fine but aparantly that doesnt mean anything.
Please help
Tom