What they do is cut down the base nute by 25% in week 8, then another 25% in week 9, another 25% in week 10 and the last 25% in week 11, week 12 just water. This means the micros in the base nutes are slowly trailed off over those four weeks. I'm pretty sure they don't use any additives, just NPK and the 7 key micros in the right proportions.
So their regime from week 7 to harvest would be like this:
................ Base Nutrient ...... PK
. Week 7 .......... 100%
. Week 8 ........... 75% ............ 25%
. Week 9 ........... 50% ............ 50%
Week 10 ........... 25% ............ 75%
Week 11 .............................. 100%
Week 12 ........ Flush with water
Hope that makes sense.
If we assume a base nute with an NPK of 20-10-40 and MPK is 0-50-30 then that regime would give these NPKs:
.Week 7 ... 20-10-40
.Week 8 ... 15-20-37.5
.Week 9 ... 10-30-35
Week 10 .... 5-40-32.5
Week 11 .... 0-50-30
Week 12 .... 0 -0 - 0
Breaking down the NPKs like that allows you to see how the N trails off and the P ramps up while the K stays fairly constant, this is what you want as N will prolong flowering and give leafy buds, P produces more and more buds and the K is needed at a high level for resin production.
Hope this helps, please feel free to ask any more questions or point out any errors I might have made.
Personally, I would add molasses, kelp, humic, fulvic and aminos to that regime. If you look at a typical bottled nute range such as Canna, you would get the same NPKs with the same additives I just listed but they would cost you a load of money. The Canna A+B is the base nute and also has kelp, humic and fulvic, the PK13-14 is the MPK equivalent and Canna Boost contains the aminos, molasses and some other stuff they aren't too clear about telling us about.
I can give you the breakdown of the salts in Canna A+B if you like. PK13-14 contains only two things - mono potassium phosphate and phosphoric acid.