I totally hear ya man. A plant with 3-4 nodes should be plenty strong to begin nutes, two weeks too early. One of the main reason's for me personally waiting up to a month to begin nutes is the plant simply doesn't need it yet regardless of how many nodes it has. A month old plant, should have many more than 3 nodes, but still needs not the nutes because alas, the soil has yet to be depleted(in my case). Like u said urself, if u want the straight up best way is to let the plant tell u, not with how many nodes it has, but with the overall look of the plant itself, leaves, stems, all of it ya know?