The information you'll here (on the boards) from experienced growers, is a much better source of valid information than the guy at the hydro store with no cannabis growing experience beyond selling you everything he possibly can.

Were cannabis an evergreen (not an annual) I'd say the addition of specific beneficials are a cost-effective benefit. Otherwise the benefits from adding costly beneficials are infinitesimal. (un-noticible)

Regarding compost teas...their original purpose was to kill insects and to spray on diseased plants. That didn't work, so some added molasses, kelp, nutrients to the mix. But that doesn't really work either because of the inability to control the plant's uptake, and lockouts and leaf damage can occur.
But my biggest problem with the teas, is listed below:
(wanna kill a med cannabis user that has lowered immunities...?)

If compost tea doesn??t do anything,
then how can it hurt to apply it?
??While the scientific evidence is
certainly lacking for aerated compost
tea activity in disease control, there is a
serious, documented concern with these
types of compost teas,? says Dr. William
R. Schneider, a research scientist in the
Biopesticides & Pollution Prevention
Division (Office of Pesticide Programs) of
the Environmenatal Protection Agency.
He continues, ??It is very difficult
to do a microbial pesticide risk
assessment on a mixture of unidentified
microorganisms that could easily
contain human and nontarget organism
pathogens.?
Indeed, this risk is significant in
aerated teas that have been ??enhanced?
with molasses, kelp, and other highnutrient
additives. Such aerated teas have
been documented through scientific
research to contain E. coli and Salmonella
populations, both of which are human
pathogens. The recent deaths due to
E. coli-contaminated spinach illustrates
how dangerous compost tea applications
can be, particularly on food crops.

Compost Tea Myths

Foliar Feeding Myths