I'm a newbie here,relatively new to fish keeping and corys

Well i bought 6 cory Trilineatus on the 28/9/09,unfortunately 3 died within a few days of each other,they were very small and all appeared to have died the same way,they would stay on the bottom not moving then died within 12 hours??
Anyway since then the other 3 appear fine at the moment and have been spawning the past few weeks!!

All 8 fry are doing well,but i'm a bit worried whether i'm caring for them fully,at the moment the 2 older fry are in the 4 gal tank,complete with sponge filter,heater and airstone and a little sand on the bottom,and the new 6 fry are floating on top on this tank in a solid plastic container with an airstone in there only until they reach about a week old then i will put them in with the older ones,will this be ok?
I am worried i might suck up the smaller ones if i put them in now,i do a 50% waterchange daily and clean the bottom of both,they're being fed on liquidfry 1,frozen baby brine which i defrost in some tank water before adding very small amounts,firstbite powder food again soaked in tank water,i use a pipette to put the food straight into the tank near the fry.
I'm use to platy fry,but cory fry are so tiny

Am i doing it right?
Thanks