Full strength baby from day 1! Best part of coco and jacks. Never added calmag, and could tweak recipe if needed. Generally speaking more calcium/nitrogen, just add more part b, more magnesium, just add more epsom. Everyone has there way, but standard 321 is fine. I like to add supplements to it tho as well, silica, fushsh!t, fulvic during flower and bud candy. But yes it was hard for me to adjust but my seedlings got watered full strength from day 1, dont worry they will love it. Still need to go easy for the first week of life, not water daily i mean. After that i watered to runoff
I have run Jacks 321 with coco and AutoPots with great results. I would fed at the suggested levels on their 321 nutrient chart, which is pretty much the amounts you mentioned. If using the recommended levels, I doubt that you will have any problems with cal mag deficiency. Sorry I can’t give any advice on PPM levels, as I find the different PPM scales confusing. I just use a good EC meter. The biggest thing with Jacks is to completely mix the part A until dissolved. I use a dark blue bucket so that the undissolved nutrients will show up easily. The other two ingredients dissolve fairly easy. As you stir in a circle then stop the undissolved nutrients will gather in the center of the bucket, just keep stirring until there is just a couple of little flakes left, that will not dissolve.
I’m only on my fourth grow now but I have only grown in coco with Jacks. I didn’t do any grow for an entire year and when I started my current one. I tagged a couple of the smart folks here to ask if they were still feeding the same ratio. So I started this grow at 3.6/2.4/1.2 and made sure to keep my PH correct and get good run off, always fed full strength. At the flip to flower I did a 2/2/2/1.2 ratio adding MKP last but only for 3 weeks. Since then I have been using 4 grams of part A and 2 grams of part B per gallon with 1ml of Tribus original. My plants seem to have done great through all 3 feed ratios, but apparently that last recipe with no epsom salt still has enough magnesium for my girls anyway. There is a you tube video from greengenes garden where he shows all the nutrient amounts of different nutrient lines for comparison. I will probably continue just feeding at the 4/2 ratio with Tribus per gallon from now on, start to finish. My ppms are 100 to 150 ppms lower with that recipe.
Ive been using jacks 2 years now. The only issues iv ever had was due to not getting ph right( 1 time). Was an easy fix. I mix 5 gallons at a time so part a is 18g epsom is 6g and part b is 12 g. I put 18 g of part a in a clear solo of water and let sit overnite so dont have to stir endlessly. I do this in separate cups for all parts. So when i mix i pour part a in a bucket of ro water mixwith a drill and paint mixer while adding the dissolved epsom and the the part b the same way. Mixing goes so much quicker this way. I mix as 5 gallon batches but mix 10 buckets at a time so this way is smooth.
Easiest way i find to mix the nutes is with a pump. Can mix as much as you want at once. I do only ten gallons at a time. People like wave makers but a pump is alot better imo.