水草情迷

I looked the website selling full series of ADA products which posted here.

In the website, it said that the ingredient of step 1 & step 2 does NOT contain potassium? Will it be a problem for only using either step 1 or step 2 with no potassium supplied? Does it need to use with the "Brighty K" together?

For water change, how much fertilizer should be use for step 1, if together with brighty K per litre for almost shaded plant?