Leaves curling is sometimes called "Cupping". It's always caused by... too much water. I'm a dirt grower too.
When the tips do what yours are doing it is called "Tip Burn". That is caused by feeding WAY too strong. You'll do 100x more damage to a plant by making that soil too hot than you will under feeding. Under feeding can be fixed. Die back from over fertilization is something you don't come back from. You just hope there's enough of the plant left to finish.
Here's the rule of thumb. Until your plants start showing signs of nutrient deficiency (leaves lighten up in color is the first easiest "tell"), you do NOT feed any nutrients. Keep plenty of Bloom nutes, Cal Mag, and microbes on hand. You'll need them. My plants typically do not need anything in the way of nutes until their 2nd or 3rd week of flowering. I'll give small weak supplements from time to time, especially after transplanting or trimming. But even then it's Ferti-Loom's clone/transplant weak ass stuff to foster new root growth. More roots = higher nutrient uptake = maxxing a plant out. You can't give the plant more than it can take in so over feeding? Bad. Very bad.
PH your water. PH your run off. If you get those two right, then your soil will usually lock step to what you want it to be unless you have something really funky going on with your soil mix.
A couple more things. I'm old so you just sit there and listen lol :) Joke. I am older but I've been doing this for a long time. I don't have all of the answers. Shit I don't even have all the questions lol. But I had a GREAT mentor, and those basic lessons have really helped me out a lot. So here are a couple of suggestions for you IF you have the ability to just fuck off with a grow.
1) If you can use sunlight, do it. Even if you are on 18/6 or more for veg, if you can haul them out when the day breaks and haul them back in when the sun sets I encourage you to do it at least once IF you can do it safely. I have a couple of 4x2 fixtures that finish out the veg cycle inside for me each day. Don't get me wrong. I'm ALL about performance. The reason is all of these lights try to replicate... sunlight. I can show you frosty nugs on the vine right now that have flowered in 100% natural sunlight but have been brought inside and stuffed into a dark space for 12 hours each day. Yep. A pain the ass. God bless grow bags. You can't outshine sunlight. Idfag what they say. If you've got good sun, learn to use it.
2) Get some shit street seedy weed. Get the seeds together. Float 'em. Plant the ones that sink. Alan used to call these "abuse plants". They are cheaper than high quality seeds and you get some smoke (albiet shitty). You want to experiment, see how your skills REALLY stack up? Get some frosty nugs out of THAT shit. Play with pollination. Stress the SHIT out of them. Find out what it takes to force a hermie. Do LST experiments. Like strings with fishing weights or wine bottle corks. Tie downs. Tie ups. Pinch them, cut them. See what happens when you cut off all of the fan leaves. Or cut the growth shoots and leave the fan leaves on. Hack it down to 1 node. Make them twist like fucking pixie sticks. Transplant and root trim. Play with nutes, supplements, micros, macros. Fuck 'em up.
3) Grow 1 plant out of each strain naturally before you start fimming, soging, training, splitting,
grafting. See wtf its natural characteristics and strengths are before you start going all "1lb yield bitch" on it. Example: The old school White Widow is a predominant sativa/indica hybrid. That beautiful strain puts out a big ass cola up to 12 inches of it. And they are FAT at the bottom part. I mean holy fucky chunky monkey fat. But then the sativa comes out and those lower nodes grow like a fucking Christmas tree. Problem is that the fan leaves cover the inner branches of the lower nodes. So nug development sucks there. To further compound the problem, unless you are SOG with monster support, the lower branches are skinny and if you pinch them, they will fall over with any weight on them. I don't do indoor fixed supports. So SOG is out. I want that plant to put out the monster cola. AND I want the lower nodes to put out big frosty nugs. So that strain gets soft bonsai wire ties on the inner parts of each branch for each node when they are younger and in veg. I use wire that has a really thick squishy rubber material wrapping them. This way the branch can grow into the wire without cramping it at all. If it needs to be adjusted, it's a piece of cake. But usually this is in the last two weeks of veg with checks through the 3rd week of flowering. Those wires both force the branch straight out from the stalk and support what I've just done to it. I can take pics if you want to see it in full bloom. The nugs at the end of each lower branch are getting huge and frosting right up. Moderate budding is happening on the inside. Why? Light can get in. The branches can hold the weight. If I had pinched that plant? Forgetaboutit. It would have been a massive bush, with light penetration issues, banished to grow 100% outside with a fucking tomato cage or wire around it. That plant is over 4ft tall plus the grow bag. 5ft total. But then again, here's a clone off of that huge plant that is in a traditional bonsai format.
4) Just have freaking FUN with it! It's just a weed. It's a fast growing, very forgiving plant. Want a growing challenge? Order a desert rose from China. Root it. Make it sprout. Dare ya...! :)
