lol...well, you can waste your money on those products or use what I suggested...most likely you have both already...baking soda in the fridge/freezer and I use vinegar to clean my coffee pots, so I always have PH up-down on hand
you will find that those products you're buying at a huge mark up are just basic shit around the house...PH up-down is 1...Epsom salts and eggshells=Cal-Mag is another...I could go on and on man, but, use google and ask what can I feed my cannabis plant if I don't have ________??? Don't just rely on this site, cuz people will swear this and that will work and they don't have a clue so you end up killing your plant/s because you took "someones" advice on a forum...not sayin' these guys, me included, don't give good advice...but there are those few...watch for how long they've been here, how much rep they have, and how many posts they have (which really doesn't mean shit
but it's a good place to start...lol...) and you can go to there page and see their posts and what people said about what they posted...peace and welcome to RIU...OH SHIT...I'm high
as for the original question "but is it too early to feed nutes yet (16-17 days old) because don't wana burn her if the soil got nutes in already?" I usually wait till the cotyledons, lil round feeder leaves start to wilt and the bottom leaves "start" to look yellowish...then I start 1/4 strength nutes and work my way up from there...peace...