Why does coco nutes often only have one A B blend, instead of 2 seperate Veg and Bloom blends?

cannabis nutrient needs don't change as dramatically as the industry would lead us to believable. A lot of what you see is marketing and them wanting you to use more and buy more. You could in theory grow something out from seed to harvest using a basic 20-20-20 miracle grow fertilizer but the results would not be as good as a tailored mix. Calcium would be lacking most likely as cannabis is a heavy feeder of Ca, The reason for part A and part B is because some nutrient lines will react to each other and participate out of solution and become unavailable to plants in higher concentrations that are in the bottles. its why you mix them up in the water first then add the other so they can dilute and dissolve into the feeding solution. As long as the feeding program your using is complete, all the micro and macro nutrients and is a good price, you don't need to worry to much. There are some better options out there then plagron but if you like it carry on, experiment later. Some of plagron products are not complete and its weird they sell em like that. Their coir lineup is complete, their soil lineup is not. or was, been a while since I last checked. Good Luck!