@Akira6063 100% shit fish will work with that product. It will work with any product. Remember it doesn’t contain any NPK. Use it every week from week Veg to flower. Doesn’t matter if you add it in the beginning or end of water change.
I’m not familiar with flower fuel but I say this it’s very high in P/K so I would only using this product from week 3 to 6 of flower (I didn’t read that anywhere) it’s just the time frame that I would bump those levels. I do have some concerns about how high your Ec / ppm will be using Grobo nutes plus flower fuel together.
Also looking at your plant it looks great but I will give it a big haircut before I switch to flower but that’s just me.
Hope this helps if not let me know