You can switch nutrients anytime you want. As long as you're giving the plant what it needs it doesn't care about brand. What can cause problems is when people don't understand plant nutrition or what's in the products they're feeding their plants. Going from one nutrient line to another isn't a big deal as long as you're not overfeeding. Mixing and matching different products can cause issues if you don't have an understanding of what's in those products which can lead to overfeeding something while not feeding enough of something else because of the different formulations of nutrient brands.
Also, that Persephones Palate is basically just a calcium syrup derived from calcium lignosulfonate. That's not going to do much. It's not going to put massive weight and density into the buds.
You don't need fancy additives to get rock hard buds. You can grow from start to finish with just a basic nutrient like MaxiBloom and get rock hard buds that are so dense they're hard to smoke. Keeping the plants healthy, plenty of light, and a good environment will give you what you're looking for as long as you have the right genetics. Chasing a bottle of this or that isn't the way to find what you're looking for.