Id imagine that your plants are still going to have the same dietry requirements as an indoor grower ...
most ferts etc provide both indoor and outdoor strengths .. cant remember how different they are .. I just ignore the outdoor levels
what is most likely is yes you could just grow outdoors without feeding .. but it depends a lot on the soil you've planted in ... and especially during flowering you might find some deficiencies appearing ...
read the grow faqs on ferting and take it as pretty much the same would be my call ...
you plants will have larger access to existing nutrients than mine do in a pot .. but MJ is a pretty hungry plant .. though perhaps thats something to do with the intensive lighting its getting indoors .. dunknow ...