For some reason I can't see the pictures above. But I agree with others that you may just need to do some tweaking and try lighter conditioners or do an occasion low-poo to keep his hair from getting too weighed down or even greasy looking.
You know, it's so silly - it's not like you're not washing his hair, you're just not shampooing it. And, after all, it's only been for the past 100 years or so that anyone's shampooed.
2C/3A/3B - mod. CG, med. to fine, normal to low porosity/normal elasticity
Current Main Rotation: MG217 medicated, GTTT or Aim2Health 'poos as scalp needs, YTCarrots or Elucence cond., Spiral Solutions Protein Trtmt & Deeply Decadent Cond., CJCCCC reg or lite, KCCC, AO Mandarin Magic, Giovanni LA Hold Hair Spritz + lots more, sporadically
HG Method: Super Soaker + Smasters-ing, brief upside down diffusing then clips or clamps & air dry. Blend gray w/henna glosses