The nutrient content is going to be variable depending on the weeds you use, but it may not be so straight cut as an NPK calculation. I sometimes rot weeds in water before composting, but use the water on crops, usually squash. They get other feeds like pelleted chicken manure, but a bit of added extra never hurts.
The liquid feed that comes off wormeries is good stuff and pre-rotted material can be of benefit when steeped in water
Have a read of this article on the main site.
https://www.allotment-garden.org/composts-fertilisers/what-is-compost-tea/People do make nettle and comfrey teas as feeds, but I wouldn't rely on mixed weed tea as a fertiliser to provide specific nutrients. You could use it as a general tonic and diluted in water, I reckon you could water crops with it year round and do no harm.
A word of warning though. All these brews stink to high heaven, so use a container with a lid and make sure you don't splash yourself with it. The smell lingers on your skin even after washing it off. Voice of experience here
I've accidently tipped comfrey tea down myself - not good