EC and PPM simply refer to concentration of elements in the solution... so a higher EC number means more nutrient. Plants can only use so much of this, and every situation is different. I could gift you cuts and in your room, they will require different conditions than in mine. Happy healthy plants need to feed more as they are growing more, so we aim for happy healthy plants. but food is not the only variable here. More important is the room. Get your temp stable and in the 70s, keep humidity around 40-60%, provide adequate light, and move the air. If you can do these things, your plants will ask for Higher feed rates, and you can provide that. if you cannot do these things there is no reason to feed too much.
I can tell you are somewhat new, so im answering more than i should. All this info is in a thousand grow diaries and such. Nute companies, all of them, are in the business of selling their nutes, so of course they tell you to use high doses. it is quite common knowledge that as you begin, as the plants require less food, as you learn to grow, never use full strength nutes. that info is everywhere. I'm surprised you have made it this far into growing and have not come across that. Look up something called KISS or lucas formula for soil. This will give you ideas of what mL per Liter or gallon of nutrient guys are using. read journals, often guys will tell you how many teaspoons per 5 gal or mL/L, or an EC level, or sometimes they ever break it down as ppm of each major and minor nutrient.
I simply add what i need to add in the way of supplements and such, then add enough base nutrient to get me to my desired EC level. I double check pH and EC after a good mix, then water that in. I'm using microbial life in my root zone ot make the most of my feeds, so i feed less in general. I feed just enough to get a bit of tip burn, then back off.
remember as the plants grow, you need to gradually feed more. but gradually. there is no magic, only happy or sad plants eating more or less.
