Aggressive goldfish?

[beettoo92]

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3 days ago I bought this pair of 'goldfish' from a roadside vendor who had them in polyethene bags rather than proper tanks and kept tapping them to show me their health and colours from all angles which obviously was stressing them out. I added them to my 65 gal which cotained 4 platies(all female) 1 platy fry(1cm) 3 mollies(1f 2m) and 2 'fry' who are both three months old and about 2.5cm long (both female, if they can be correctly sexed at this time) and also 8, 15 days old molly fry.
So these new entries are pretty freaked out and crash into the other end of the tank as soon as they see anyone approaching. Now today when i woke i saw that one of my platies is dead most fins missing, the other three also have lots of fin damage and are totally traumatised infact one was stuck between the tank wall and the internal filter(rated 1750g, gave 600-700g when i measured it). The platy fry is also missing while the mollies are all ok just avoiding the new comers a little, though the fry are getting chased but they havent receded in numbers nor any seem injured. mollies and platies are the same size.
Is it normal for goldfish to attack platies like this?
I would beg your pardon if these are not goldfish or some specific strain.

[beettoo92]

840724_1316961944362_full.jpgHELP!!!!!!!!!!!!!!! somebody........... anybody......help......