its just name brands... it always boils down to N, P, K.
the plant dont give a shit about how much money u spend and how great other growers have done with it, its just wants you to feed it the right amount at the right times..
with that being said i agree with others when it comes to brands are made to be with each other, such as try not to be using 5 dif brands, but i know there are people out there that do it..
just do a flush like others have said which luckily with DWC is just changing the water couple of times (assuming u know the flushing process)
the moral of the story, keep it simple, give it N, P, K, and all the macronutrients for the toppings.
good luck