Jenn Aire Side by side Fridge side luke cool. Poor... I have a Jenn Aire SXS Model # JSD2789GES

Question

I have a Jenn Aire SXS Model # JSD2789GES experiencing cooling issues on the fridge side. After seeing other posts I have taken the panels of to find I had icing on the coils and up top near the icemaker. Additioanlly when I checked the back of the fridge the I was LOADED w/ dust on the cooling coils as well. I have cleaned all and defrosted. Do you think this is a cleanliness issue or a defrost timer issue? Thanks for any help