You can use Top·Max with nutrient-rich organic soil, but I wouldn’t expect it to magically improve the taste. It’s primarily a humic/fulvic-acid-based bloom stimulant, not a conventional heavy NPK fertilizer, so used according to the label it’s much less likely to cause classic nutrient burn than simply adding more base fertilizer.
But if that manure/humus mix is already feeding the plants beautifully, “they need nothing” is a perfectly good strategy. Adding products just because flowering has started can sometimes create more problems than benefits. And flavour/aroma will depend much more on genetics, plant health, maturity, drying and curing than on adding Top·Max.