I've never seen any LEDs with a forward voltage drop of 3V before. What colour are these LEDs?
If they're infrared, red, orange, amber, yellow, or yellowish green then they'll work but if they're blueish green, cyan, blue, violet, ultraviolet, white or magenta then you'll need a higher voltage.
Sorry it's hard luck you need a separate resistor for each LED. this is unless you're certain they were all manufactured from the same piece of silicon and only the manufacturer can assure that.