wonderful photos... I'm no expert myself, but i would add some fill or flash... of course i would decide this based on the sync speed of your camera, and given that you mostly use natural light, reflector is the natural answer....

btw... the 1st photograph is my favorite of the four... moreover, i think the focus is fine and the shadow/darkness of it is awesome... putting a fill in here, would ruin the mood of such a photograph, which i see is somewhat prevalent here.

i mentored with a photographer who went from medium format to digital with many years of experience, the thing he always emphasized was catchlights (of course in the case of photo 1 and many others on your website the photographs don't call for catchlights).. I think for those that do merit in some fill light also deserve some catchlights.

all in all, those are awesome photographs.