I'd advise DIY unless you've got enough money that the difference between $50 and $360 a year means nothing to you.
You won't learn anything using ADA's cocktail. You will consume their product, and if it changes or disappears, be left at their mercy or back where you started.
Yes, it grows plants. But why would it magically do better than anything already known about plant nutrient requirements?
Here's a very nice DIY fert EI tank:
Would you complain about that sort of growth?
-Philosophos