If you already use ewc, leave the dry nutes, if you put enough ewc from the start you can finish your grow on only water if the pot size is big enough.
In the worst case, you just add some ewc to the top of the pot once a week and water.
When you start mixing all sorts of nutes you create unbalanced NER, and that roots don't like.
Coco with only salts is in my opinion the best way to get consistent results, I like to add ewc because it has so many elements salts don't, and it does have a profound effect on terps/smell etc.