Ok, so your coco should be buffered before you even use it, Do you know if the coco you are using is just washed or if its buffered, there is a big difference in the 2, or are you buffering it before you use it?
Here is my understanding , So coco's cation exchange complex is naturally saturated with sodium and potassium, washing can only remove little of this as the bond between the coco and elements are to strong for just water to remove, Thats where buffering comes in. saturating the CEC with Cal/mag and iron. those are the 5 elements at play sodium/potassium and cal/mag and iron.
Coco is generally a negative charge and is naturally full of sodium and potassium, which is bonded to the coco saturating the CEC, So what we want to do is remove that, we do that by using cal/mag and iron, by saturating the the coco (CEC) with this for a period of time we exchange the sodium/potassium for cal/mag and iron, because they have a stronger bond to the coco displacing the sodium and potassium to be rinsed out.
if this is done properly when you feed your plants there is very very little exchange of calcium nitrate, Magnesium and iron , because the CEC is already saturated with it, So what you feed goes to the plants not the coco.
if this is not done, when you feed your plants the calcium nitrate, Magnesium and iron is being exchanged in the CEC for sodium and potassium because it has a stronger bond to the coco, so the feed for the plants cal/mag and iron ends up going to the coco, and sodium and potassium in the coco is displaced into your feed for the plants. making a mess of things
I haven't used coco in awhile so I'm not sure what its like anymore, but when I was using it I found even the buffered coco wasn't buffered to my liking, I found it a pain in the ass washing and buffering it thats why I went to sunshine.
If want to know about mixing nutes its easy and plenty of guys on here to help, If you want PM I can give you some info, and recipes in g/l so you can mix any size batch you want. once you learn how to adjust it you can dial it in to whatever you want, but you'll also be able to make a seeding mix , veg mix , pre-flower mix and flower mix and not have to add anything extra as it will all be in it, other then microbes, and enzymes, the only other things i use is fulvic and some kelp, I play around sometime with other stuff but I really don;t thing it is needed.
hope some of this helps