Hey Kushleaf, looks like you are getting some good answers here to your questions. I had a look at your soil, that John Innnes looks very nice man! Wish we had a quality soil like that for purchase stateside. So having no idea what you have available and what you are able to purchase locally or get shipped I decided to paste some of my note here for you to have a look though. If you follow this mixture it should give you a pretty good soil that will only need watered. The caveat here is this hasn't been tested with autos so be cautious when adding your amendments. It may be safer to err on the side of adding less and amending more later in the grow than to be too hot and kill your transplants. Or you can always mix the bottom half hot and use straight John Innes in the top half so your plant has time to grow into the hot soil.
Food Mix - contains equal parts (by volume) alfalfa, fish bone meal, fish meal, bat guanos, comfrey, dandelions, etc. This mix is intended for amendments used as 'heavy' nutrition. When mixing up a new batch of soil, apply at a rate of 2 cups per c.f. from this mix. The main thing to keep in mind here is to try and keep the NPK ratios inline with each other. In other words, don't use all bone meal and no blood meal or what have you. You want your ratios equaling out about the same or if anything, go lighter on your N because you can always use fish hydrolysate added to your water throughout the grow to boost some N very quickly which is what I do.
Fix It Mix - contains equal parts ( by volume) of neem seed meal, karanja seed meal, crab shell meal, kelp meal. Use kelp meal at twice the volume of the other amendments listed. This mix is for alleviating any slight deficiencies or just to add a bit of nutrition and pest control during the grow. When mixing up a new batch of soil add at a rate of 1.5 cups per c.f.
Mineral Mix - contains equal parts (by volume) of the amendments intended to provide trace elements and minor amounts of macro nutrients. I use azomite and oyster shell powder in mine but adding greensand will boost your potassium if you have it. Use at a rate of 1 cup per c.f when applying to "new" soil.
The other's category:
The biggest one here is rock dust - I cannot state enough how valuable this amendment is in this style of growing. It helps provide much more than simple nutrition; it provides stucture, anchors if you will, for fungi to attch to and grow from. Use at a rate of 4 cups per c.f. when mixing a new batch of soil up.
I also use some langbeinite (Sul-Po-Mag, K-Mag) at a rate of 1/4 cup per c.f.
You are going to need a buffer of powdered lime and gypsum, equal parts at 1/4 cup per c.f. also that will help keep your pH in range.
Lastly, I really like adding calcium bentonite to my mix as a way of boosting cation exchange and adding more available calcium to the mix. I don't know how well it will work using a premixed soil like John Innes because it does have a tendency to make your soil clump up a bit so I would skip it unless you have something else to balance the soil with. It also isn't the easiest product to find locally for me, I have to order it online.
Hope that helps and best of luck!
) I thought you may bite! ...Although I`m glad you asked mate...I`m all good with Hippys (as long as they`ve been `sheep dipped`...b4 supper! :smoke
. Sorry if I offended your sensibilities my friend, I was just feeling mischievous! 
You didn't offend me but I grew up in that era and had shoulder length hair and wore bell bottom pants,smoked dope and drank wine back in 69,it was a mighty fine time.
