What kind of nutrients is required for growing a healthy plant?

Hi fellow growers. I have a couple of questions regarding nutrients and soil.
I started this year growing 2 autos which both suffered some problems with nutrients/ph-level.

I grew them in a 15L medium with soil, cocofiber and vercu. I don’t know if it was a good idea mixing soil and cocofiber in my medium, but I did not want my medium to get to strong with nutrients. Thats why I added the cocofiber as they contain less nutrients then soil. Was this a wrong move?

Next up is nutrients, both plants where fed with the 3part solution. They were fed with Micro, grow and bloom from T.A + CalMag. I fed them with nutrients twice a week from week 3 of life. Hear is my dosing chart. The nutrients were mixed in a 4L bowel, with about 2mg/CalMag - 2mg/Micro - 1mg/grow - 3mg/bloom. They seemed to love it in the beginning. But towards the end they suffered from yellowing leaves from top and then spreading down. Could my feeding be a problem?

What about PH? Since I was growing mostly in soil I didn’t think PH would be a problem. I have been reading a lot online regarding this topic, but people seems to have different opinions when it comes to if you need a ph meter when growing in organic matter. Should I buy one for the next grow? I think so, just be sure I am doing it a 100% correct this time.

What brand of soil? How much coco did you mix in? Total feed ppms? Did you water to runoff? Got any pics? Sounds like nutes built up in your soil, but thats just a guess..

“Nutrients” are required to grow healthy plants but you do not need to provide them from a bottle unless that is your preference. The problem with ph is a lack of understanding what it really means. What many do not understand about ph is that in a bagged organic soil that already contains everything that is needed by the plants the ph is already set. All you do is add water. What regulates ph in a soil grow is the level of microbial activity and the composition of the soil. This is why compost is super important; e be more so than npk and mineral inputs.
This is why wine grapes from different regions are slightly different: the mineral content, presence of fertilizer, amount of rain that particular season, etc etc can all have affect on the sugar/moisture/alcohol content of the grapes. This is what each vintage represents; sometimes there is an exceptional season that makes really good grapes that year. Sometimes the grow season is not as good for what ever reason.
That being said coco coir is inert. It has no npk value or effect on ph up/down. This is why you must adjust ph in the proper range of absorption when using straight coco as a grow medium. Plants cannot absorb nutrients directly unless the solution they are in is in the proper ph range. When coco is added to organic soil it will simply cut the mix down and make it weaker which is maybe why you saw your plants fall off after a time. It’s not easy to keep living soil active microbially unless compost is added regularly in solid or tea (soluble) form. Bottled nutrient gets around this but ph must be adjusted. 2 part nutrients are not organic meaning they slowly kill off the microbes in your soil that regulate ph. So you have 2 choices: forget about ph & stay with organic soil and water with clean water only & compost (teas) or use your mix as a hydroponic medium and adjust ph every time you water/feed. No don’t buy a ph meter unless you are doing a hydroponic style grow.