i like foliar feeding especially if the plants seem to be having any issues getting the nutrients from the root system, ie; you are trying to help them to recover more quickly from a pH imbalance and/or nutrient deficiency.
Also, it helps the plants to 'get a bath' now and again to remove dust and dirt from the (stomata?) the pores or what have you where they breathe and such, making sure to do both the top and the undersides of the leaves. i'd recommend this at least once a month. and the same thing can be done toward the end of flowering i have heard to help to draw out unused nutrients (though you also have to worry about mold and bud rot at this point... so, buyer beware).
