This is from the Jacks Classic grow guide on tomatoes:
• You may want to add about a teaspoon of Epsom salts to your applications of 20-20-20 to provide some additional Magnesium to the plants nutritional regimen. Magnesium is part of the chlorophyll molecule and obviously very important in the process of photosynthesis.
So I think you are right in wanting to supplement there, but in keeping it simple and cheap, you might want to consider the epsom salts, dirt or shall I say salt cheap?
I think superthrive has a place in rooting clones and transplants but beyond that, I don't think it has a noticeable effect. If you really like it, maybe use it as a foliar feed?
I haven't decided on using molasses or a sugar supplement, probably not the first run, so I'll have something to compare it to.
I believe in the silica supplement wholeheartedly, especially since I plan to make these branches Heavy with big buds, I think the silican blast is like 50% or more silica? But it's freakin expensive too. I'm thinking about the Dyna gro protekt, but it's only like 7%, I believe but cheap? I think I'll start with the cheap and then if I do decide on the expensive, I will have a reference to decide if it's worth the extra dough or not.
I am also going to supplement with dyna gros 'Grow' formula for the extra micros, if and when needed. Maybe every 3rd or 4th time they get nutes. I noticed that Riddleme did this with Matilda.