Yup. Get the soil tested! I'm happy to do it.
+1
Fish emulsion I use for younger plants and dilute it heavily with filtered water. Water in .. I do not follow the label recommendations. My grow space would smell like a fish stand if I did. So maybe 3 times in the grow cycle but early.
Fish emulsion is not my go to... I prefer worm castings & ground up re-hydrated kelp meal... again both diluted heavily in filtered water.