When fertilize seedlings?

I have some seedlings that are 1 wk. old. They have their second pair of leaves. When should I start to fertilize them? I am thinking 1/3 amount and move up slowly. The plants are growing in different media, some are in potting soil, some in a Perlite vermiculite blend (50-50), a couple in coco chunks, and finally a few in DWC.
Thanks in advance, this site is really a great source of information.

VM

wait 3 weeks unless it shows you it needs it.

darkdestruction420 said:

wait 3 weeks unless it shows you it needs it.

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Should the coco and perlite/vermiculiite mix be fertilized at any earlier date than the soil containers?
Thanks,
VM

add gardenlime too ,cocoa,soil mixes...I like to use a low dose liquid nute 3rd week .........

you might need some lime in the coco. But still wait till they want nutes