From what I been reading is that you want almost a neutral soil for the top and midway of your soil in your pot and a more nutrient balance soil on the bottom . By layers of your soil it really gives your seedlings a better chance through they growth cycle and as they roots develop you don’t want young root developing plants in hot unbalance nutrient release soil , or it will cause all kind of nutrient defiencies . Now I’m no expert , actually I’m in the beginning of the learning process myself . I started with 3 bag seeds of some decent street bought , but I started off to anxious of giving liquid nutrients in fox farm and ocean forest mixed soil which I learned had all the nutrients the little seedlings needed . So I actually burned 2 of them to the point of no recovery and been fighting trying to save the one , but brother this plant has been stressed beyond help , but somehow pulled through through a very intense flushing method and a pot transplant from a 2.5 liter to a 3 gallon , it might just make it to flower with this new method I have learned about layering your soil from neutral to balance soil in your pot . But per say if you want to add nutrients yourself , I suggest you start with coco coir mixed with a great decent amount of perlite so it can drain properly . But if you used fox farm happy frog (the brown bag ) it’s a good soil medium to start seedlings but "DO NOT " add any liquid nutrients until at least between the 4-6 week or until the plant has accomplished at least 6 - 8 nodes . The way I do it is by the fan leaves . The first set will be 3 leaves , the second set will be 5 , the third will be 7 and the forth will be 9 , and usually after the ninth leave development it’s has the ability to be topped and can be still vegged until the next layer of leaves grow from where it’s been topped , and once you have reached that point , I say it’s okay to introduce the plant to liquid nutrients , and always start with less than what the bottle says are you can give way to much of nutrients to soon . Now at this point if your are seeing the plant show great response a vigorous growth your doing good . But make sure you don’t try to rush the growing process , it has stages for a reason , so be patient and approach with caution . Now if you growing indoors and your plant reach 18-20’ you can switch it to flower 12/12 and after the second week of switching cut back on your veg nutrients and slowly introduce your flowering nutrients slowly …baby steps to prevent problems . Now the easiest way I was told is to transplant in stages . Seedling from cup to at least a 3 liter pot with just water schedule , and from a 3 liter to a 3 gallon with just ph water , and from a 3 gallon to a 5 gallon with ph water and liquid nutrients maybe 3 feelings and the plant could finish to harvest without many issues . Now you will need measurement gauges tds meter ph meter and balance water ph between 6.2 -7.0 in the water run off and you could become successful . But honestly you will have to keep a watchful eye on your plants , it’s merely best to know the strain you growing and what best environment it grows best and try to apply that climate , humidity , temperature , ph ratio at the roots and parts per million that’s moving in the water to kind of keeping a handle on things , but it you layer your soil in stages and plant your seedling in the right layer mix it will do good all by itself with just balanced ph water run off at 6.5-7.0 I believe from my experience , but that is not all that great right now . I myself is still trying to reach success , but I have been reading a lot of information and Roberts grow bible daily . My best suggestion is not to over think to much , give the plant the right elements that it needs and you can end up with a few ounces for your first grow. But good luck to you , have much patients , and learn to read the plant , because they actually will tell you what they desire . Be very selective with your nutrient system less is more , baby steps with liquid and know what’s in your soil medium , learn to mix it properly and you could do great . It’s a very strategic precise learning experience and every strain is different …hope this help you brother and hope we both one day can be hanging and drying trying to fight the smell waiting to smoke our personally own home grown medical smoke !!!