Some of them will give you harsh and tasteless weed. You need to find the product that gives you good weed not just the cheapest product. And yes there is a difference. You sometimes get what you pay for.
Learning about nutrients is a wise investment that will pay dividends for a lifetime of growing anything, not just cannabis. There are lots of great threads on the farm that discuss nutrients, and this barely scratches the surface. You will quickly realize that ferts are ferts, and that you can get them a
lot cheaper than buying them by the gallon at hydro stores. I run Jacks myself and I couldn't be happier.
As far as harshness? Only part of this is how to flush properly. Learn how to balance your nutes, so the plants get everything they want but not too much of it, and so you can compensate effectively for differences in strain and growing condtitions. Learn how plants absorb their nutes in various environments and media so you can improve their uptake rates and therefore yields and quality.
Tasteless? The single best thing you can add is sulphur. This is a basic building block of many of the aromas and cannabinoids we're all doing this for. Epsom salts are an excellent source of it- and magnesium, too- and it's inexpensive and widely available, as close as the pharmacy section of your local grocery. As a starting point, I would add 2mg/gallon to your nutrient solution. Dilute it well before adding to your reservoir, as sulphur and calcium love to get together, bind up and drop out of solution, creating... gypsum. Same stuff as your drywall. See? You learned something already!
Another closely related path to investigate more closely are the worlds of NON-fertilizer additives and beneficial microbes.
Triacontanol is just one of thousands of these. Some nute lines have them, and some don't. Rarely is it listed on the bottle- not because they can't list it, but because they don't want to spill the beans about the details of their proprietary blends. Again, many threads on the farm offer a wealth of information about what they are, how they work, why you might- or might not- want to run them, and inexpensive sources of supply. Shameless plug: Capulator's biopaks rock!