If the rainbows are threadfins or dwarves then no. If they're not threadfins or dwarves they need rehoming. Id add more rainbows if they're a small variety.
Let the existing fish grow and the tank mature, don't be so eager to make the tank a "sardine can."
It appears some think your rainbows are Dwarf Neon, but what are your corydora? You could have well in excess of 50cm of fish in a 70l tank (minus substrate; bogwood; internal filter etc).
If you've worked it out right you should be able to do both!
Your tank is 73 litres which is 19 US Gallons so by the 1 inch per gallon rule you can have 19 inches or 47.5cm of fish.
Neons grow to about 5cm so you've got (potentially) 30cm of Rainbowfish. If the Corys grow to a similar size which they could do, that's another 30cm of fish. So in a review of my earlier post, you could argue you are already over capacity.