I follow your suggestion. Any idea what fertiliser to use though. I have been using seasol but these seedling haven't had any yet.
I haven't been feeding them anything. I do probably need more air circulation..
Seasol has hardly any nitrogen or phosphorus in it, and by comparison a good deal of potassium and natural growth promoters and micro nutirents.
While this will help young seedlings produce greater root mass initially and help with transplant shock and plant stress in general it will not be a sufficient source of food once the plants start producing more foliage.
My advice would be to get a nice gentle organic liquid fish fertiliser (Ie NPK of 2 to 3:1:1 or something similar) as this will not likely burn the young plants roots especially at 1/2 strength but will give them a nice fast boost of growth at the same time with plenty of calcium (trucker/cargo mineral) to help the plants uptake the goodness.
I use this as my first liquid fert usually (not the granules the liquid)ecofish
and ecofish analysis
It has plenty of calcium (more then potassium and phosphorus) and a good amount of Nitrogen which is immediately available to the plants, but won't burn them at half strength.
Its available at bunnings and is cheap which is an added bonus.