@Dr.Green55, I tried running EC up with Athena. I found never get it above 2.4 before the plants started to burn. I know Athena is stating an EC of 3.0 from start to finish. Every time I tried using Athena I had to still addCA to the formulation in early flower. I always had problems with Athena. It just seemed in balancedThe first thing people (New Growers) need to understand is that all these bottle nutes etc Jacks , HGV Athena are really one size fits all, and you the grower do not dictate how your plants like there food and the ratio's they eat it at, that is set by many other factors lighting intensity, LED vs HPS temps RH, rate of water uptake etc etc, so when using these products they will works differently for everyone, so your really trying to find the point that it works best for you, and that will mean different EC etc for everyone, but its so, that different ratio's will require a high EC to get proper uptake IE. HGV Athena
@Aqua Man I have never used those so I'm not sure there accuracy or how good they are.
If I was going to build a solution that had to be spot on for my setup there is really only one way I know how to do it, and thats water analysis and tissue samples, I'd start by setting my N to the amount of light temps ,C02 etc then set the ratio of Ca off that, a little under or over N ,if over you will most like not see N tox, to much Ca you'll get purple to low you will get whiteish on new leaves, k Mg etc to balance for time of grow, I would do micro's separate because I'd want to set Fe, Mn B etc individually. I'd then lab test my solution to see if the individual PPM and ratio's are mixing to what I wanted.
The only way from there to see if the plants are getting it in there optimal ratio's is tissue sampling, either every week or every other week, that will tell me exactly what my plant has in it, and what I need to adjust in my formula, I'd do one for veg and one for flower. as long as your grow environment, lighting media etc stays the same it will be good. fulvic, silica etc will all be foliar spray.
depending on the scale i'm not sure i'd spend thousands on a pens to tell me whats in my solution, I can get lab tests done for 40 buck i'd go that way but you may not have that option
edit I took a better look at those pens and they do, do tissue as well , if they are accurate and will last a long time maybe but there a lot of money, again depends the need and scale, the balance for me is lab testing can be done cheap. I don't know what the cost would be where your at