Orchid food is for orchids, potted in orchid mix.
Hydro pot food is for pot potted in hydro.
They are buffered very differently, and have different relative nutrient levels. You'll be fighting with pH and lockouts if you use the wrong fertilizer.

You don't absolutely NEED an EC meter to grow weed; I've done without on my crappy city water, but if you can't play mad scientist, you gotta play assembly line dude... take the parts that someone else tells you to use and assemble them EXACTLY as intended. Just as you can't put a small block in a Volvo without modifications and a good understanding of the whole system (but OH HOT DAMN is it ever worth it OMG), you can't grow hydro with soil fertilizer unless you have the tools to make the necessary adjustments.

So in your case, match like to like. I strongly recommend the Canna Aqua series as being virtually impossible to fuck up if you follow the instructions on the back of the bottles.