shouldn't have a major issue... i'd use the one up then switch, sure... i wouldn't use both at the same time - that would be bad idea for any 2 nutes at instructed doses.
the good ones will all be fairly similar, anyway. If any of the organic stuff is slow-release in effect, not necessarily osmicoat-like stuff, you may need to adjust your GH products as it transitions. The organic stuff isn't as plant-ready as what you will be feeding with the GH hydro nutes, so there may be some lingering added nutrients.
be a little extra religious about maintaining a 10% waste runoff with the hydro nutes. Any transition will be minimized quickly.