Why they grow so fast

That'd be pretty small for 4 weeks. Looks really good for nearly 3 weeks (6 nodes?)... if doing things right, genetic variation is the key here and no magic prodcut that circumvents it.. you either get most of the potential growth or you don't based on how you handle it. it's not the foliar spray, lol.. i guarantee that. maybe you just have a better ratio of nutes than before or better aeration/drainage properties in soil? rain water is an unecessary and very often less than optimal option for rain... turns out "natural" doesn't really mean what people percieve it to mean, lol. get all sorts of pollution and heavy metals in your rain if downwind from any urban center... which pretty much encompasses most of the world as far as where people live. i don't see clawing.. the last 2 more recent pics look healthy plants. leaves are praying and 'flattish' .. you'll know more about your fertilization choices for this grow in the next month an a half... it's easy to look good early on. the faults of ratios and concentrations display over time as rate of provision doesnt' match rate of use properly. (IF it doesn't)

You had a ph issue early on the twists in your leafs show tat. Also the clawing shows too much N. Which could be caused by imbalances in ur ph as N is the more easier element that can be taken up in ph swings easier than others. Reason y N is a issue for many new growers.. If you're In soil. Cut back ur nutes or feed less frequently and more follow up feeds. Rain water needs to be treated. It can have all kinds of stuff In it picked up in clouds. And would have a really high ph (is wat I mean by treating, ph,in) She's not looking too bad. Stop spraying it also..Once your plant has developed a root zone it doesn't need it. It'll lower o2 intake by blocking stomata vents.

IMHO they are perfect size for their age