I've been running at 80% strength. Which it seems to work great for most plants but out of the whole tent last run, 2 had an issue once flowering started and my current plant has the same issue. Less severe this time so I'm not sure what caused it. MoG gave me some advice on running just the part A with the soluble gypsum for Cal as the "B" from Jacks has a lot of N. Also add the epsom salt as normal. I'm just waiting on the gypsum to arrive.
That said,
80% strength is actually the 321 ratio 3g A : 2g B : 1g epsom
I bump the epsom to 1.3g/gallon
Usually ends up around 700-715ppm / gallon
You could certainly try bumping down to 60 or 70% and see what works for you. I think that is likely MoGs suggestion with the 600ppm dilution. I did not find much information on autos with Jacks.
@Cave Dirt Cody seems to absolutely kill it with whatever he uses.
There is a chart with the math already done here: