This my first time with a 5x5 tent, coco, and AutoPots. So I figured, what the heck might as well give Jacks a try also.
Here is some of what I have learned about coco so far. I am running Mills Nutrients, and it is a good well balanced nutrient. When starting the plants in coco in drain to waste containers. I had to mix the nutrient solution to an EC of 2.0-2.4 in order to get them looking healthy and green.
But I quickly learned that this level was too high for the bottom feeding AutoPots. I am presently at a 1.4 level, and it appears that it can even go lower.
When I switch to Jacks 321. Should I pull out a calculator, and start off with
75% of the recommended 321 amounts, (for the AutoPots)?
I saw a picture of a chart on the Jacks’ website, and it seemed to imply that you should reduce the amounts for bottom feeding. But couldn’t find the article that the picture came from.
Seems too make sense, in absence of run off you can and should reduce EC.
I run full strength Jack’s from two weeks to harvest. Silica should be added too: I like having my nutrient solution at or around 900 ppm (1.8 EC). It will get bumped up a bit in flower and I do a 2-2-2-1.2 of MKP for the first three weeks at transition.
I run my auto pots, coco and jacks almost identical to @Myfriendis410. I’ll occasionally have a plant that likes it a little lower but never below 800/1.6 
@Myfriendis410, @OGIncognito, Thanks for your replies. It looks like I will be shooting for an EC of 1.8-2.0 to start with. At 10 days since the light flip, I don’t want to underfed either.
@Myfriendis410, is this the MPK that you are talking about? If so could you elaborate on how you apply. Do you you this instead of the Jacks bloom food that is on the 321 schedule?
ICL PeaK MKP fertilizer 1 lb.
PeaK (MKP, monopotassium phosphate, KH2PO4) is the last word in specialty fertilizers for hydroponics, fertigation, foliar nutrition and special starters. PeaK is a solid, fully water-soluble PK fertilizer containing 52% P2O5 and 34% K2O, making it the most concentrated commercial fertilizer known (P2O5+K2O = 86%).
Right at the flip for 3 weeks the normal 3-2-1 ratio is exchanged for 2-2-2-1.2 with the 1.2 being MKP. So: 2 grams of Part A, Part B and Epsom with 1.2 grams of MKP. At + 3 weeks from 12/12 I revert back to 3-2-1. Silica is used from start to finish.
I do not use the Jack’s Bloom Food.
@Myfriendis410, Gotcha, I have bought Jacks for the 12-4-16 and 321 schedule. When I restart next time, I will use the 12-4-16 and 321 with your recipe for bud set. I would think a pound of the MPK will be plenty.
Is your water source RO?
Yes, I have RO water.