There's so much wisdom around here about when NOT to use nutes... When SHOULD you use them? There are entire websites dedicated to nutrient deficiencies, with pictures. Newbies get ridiculed for adding nutes too early. I've been reading these forums for months, and I've never seen a thread/post that says "here's how I knew they needed ferts!" How do you know when they're hungry? Age? Node development? Does growth slow down or speed up? Can you tell by looking at them?
I've seen some people add grow formula nutes as soon as (or soon after) the vegetative stage starts, after the third set of true leaves forms or so. Bloom formula nutes are usually added once the flowering stage is initiated, which is usually after a month or so of veg growth.
I'm just guessing but I think a good time to start adding light nutes is after the third or fourth node of branches arrives.
It's been a little less than two weeks for me, and my little ladies sort of stopped growing, and started going slightly more yellow on the leaves, as well as red in the stems. For the first week, they popped their seeds in 1 day, popped out of the ground in two, and have basically grown like pros. I read a few places that said these are classic signs of nutrient deficiencies, which is weird because of such a young age. Since I'm using regular soil w/ no added nutes, and have decent drainage I can only assume this is due to lacking nutes. I decided to feed them some nute mix at 1/4 strength. Hopefully they get happy again. I am however nowhere near a pro, so I am not to be seen as a source of reliable information.
you did the right thing. i start feeding mine after about three weeks of veg. growth and definitely 1/4 strength. i've nute burned my freakin plants soooo many times!
i didnt read anything abvoe me so idk if someone said this but 4 weeks into the grow should be good and dont voer do it