OK heres the potential problem...
It may not have acclimatise themselves in time before u went on holiday
How long have u had them...and most important question...did u ever witness them eating and consuming the food ?
They are sand sifters so some foods that go in their mouth and if they dun like it, they will eject it out through their gills...
So the food may go in the mouth but not necessary they eat it.
And in a goldfish tank...i dun think there are any food for them to eat...goldfish pellets are floaters and corys are bottom feeding fishes...so there is technically no way i can think of that the corys can get any food...
They need constant food...but if u dun feed for 2-3 days, they can still take it.
Wat i am afraid happened here is that they did not have enough food when they are in the goldfish tank.
They can last a week or two without food by the way...
so now when u put them into the community tank, i guess they just ran out of gas and puff out...
Nothobranchius are only vicious to own males and they are attacking the corys because...they are opportunistic feeders and the cory is a slow target...the max damage they can do is fin nip it and stress the cory out...nothing more
corys are armoured catfish and are well defended...so from a notho attack...

good luck for the notho jawbone lor
Well, corys prefer to live in a school...if u get like 10 pcs of cory, they be more than happy
And ar...dun feed algae tablets only...cory are not supposed to be vegans...u can try those sinking tablets from sera which u can stick to the glass...they go bonkers over that food

cory feeding frenzy

or a cory ball