it's totaly fine to mix companies. But dont mix different compaines 3 part grow/micro/bloom. What i mean to say is dont use Bloom from General H and Grow/Micro from advanced Nutes. Probaly not a good idea.

Also, Dont use two of the same produce.
So its fine to use Advanced Nutes G/M/B and General hydro bloom booster
but it's not cool to use advanced nutes bloom booster and general hydro's bloom booster

I mix organics and synthetics and just grew the BEST WEED IVE EVER SMOKED. and i'm from BC Canada, so i think that says something.