Is it OK to use Advanced nutrients Big bud coco on soil?

There's risk you provide too much of the trace elements or possibly any and all... coco requires 100% of nutes to be provided. Your soil has some nutes in it. This is the difference you need to consider. if late in grow and you know your soil is sapped and you are fertilizaing 100% strength etc... That's a context where you could likely use it and have zero problems. Early on you may need to dilute it slightly more than you typically do... kinda depends on a few too many variables to give a blanket statement. I've used 'hydro' nutes in soil before with no problems. This is basically waht 'coco nutes" are... they are simply a complete feed. Now, not all products are equal.. check label.. if it is just a bunch of P/K sources.. this is not what i was talking about above... You could use that as a bloom booster, sure... i'd just calculate your ppms of what it is 'boosting' and make sure they don't skyrocket too high... you'll cause more problems than any advertised benefit. One thing to pay attention to... they usually buffer them so pH is good for a soilless substrate. So, i'd test pH and if too low you'll have to add a base of some sort to raise pH to ~6.8.