The mysterious role of potash and other promoters
Here's a question. You might have read I give my plants weekly applications of soluble potash when flowering starts. Too frequent? A friend is supplying me with earthworm juice which I'm considering putting in the potash solution. Comments?
Well, potassium has no direct role in promoting or assisting flowering in most plants, however, it's been long promoted as being beneficial at this phase of the plant's life (a useful myth, commercially speaking). Nevertheless, as a macronutrient its presence is critical at all stages due to its various roles in ion exchange & nutrient transport, photosynthesis, respiration and enzymic catalysis.
Here's a neat acronym:
C. H O P K'N S CaFe; Mighty good (but) Not always Clean. CuM'n CoZ'n MoB
carbon, hydrogen, oxygen, phosphorus, potassium, nitrogen sulfur, calcium, iron, magnesium, sodium, chlorine, copper, manganese, cobalt, zinc, molybdenum, boron.
But, nutrients don't
regulate growth; plant hormones do, (viz. auxins, cytokinins, florigens and phytochromes). Photoperiodism is understood to initiate the formation of floral primordia. Gibberellin is also critical in floral initiation.
As regards photoperiodism, where does
Cannabis sit? Is it a Short day plant (SDP) - only flowering with increasing dark (night) periods, or a long day plant (LDP), which only flowers with decreasing dark periods?
It'd be interesting (and challenging) to try to develop a flowchart of inter-related phenomena in relation to this question, as it's undoubtedly complex - you're looking at a gamut of factors including heat, water and incident radiation fluxes, enzymatic activity, phytochrome response to frequency range of incident radiation, turgor pressures, (possibly) [CO2] concentrations at stomatal surfaces, relative relationships between ionic concentrations of the macro- & micronutrients and no doubt a few other things I can't recall at the moment (mycorrhizal relationships, soil ecoflora, positive vibes and the
'right' touch, etc.

). As for the earthworm juice, I dunno, except that as a general rule of thumb, earthworm castes are recognised to be a good source of carbon, organic matter (erm, carbon again?) and a complex of microbia - I can't see how EWJ could exert any beneficial effect on flowering of these plants, but as you well know, it's great for the soil's health.
In summary, and specifically, weekly applications of potash are unlikely to be a problem unless they're at such high concentrations that you're inducing potassium toxicity - and your girls will tell you if that's the case. And given the highly fertile profile in which these babes have their roots, it's unlikely that you'll see a K deficiency, and also, that particular soil profile has a relatively good binding capacity to retain ionic K (i.e., clay component is significant). It's a bit like a Mortein ad, eh?