adding more soil on top

so I have a mother plant sitting in a 3 gallon bag with mostly FF light warrior (it was all I had at the time) and a little FFOF and perlite. the soil level has fallen considerably after weeks of watering.

my question is: if I just add more soil on top (FFOF), will it benefit the plant in any way? will the nutrients in that top soil make its way down to the roots when I water?

Yes, keep the top roots covered. It won't hurt a thing. The nutes in the soil tend to wash down with waterings.

Yes its called top-dessing. its good for your plant especially if you notice a deficiency.

Another good thing to use is some good compost. Good compost has loads of nutrients!

A great top dressing is worm castings....