I have been growing beans for 4 years now and this is the first time I have encountered this problem of leaf yellowing then browning on older leaves, not new leaves.

-Current bed has never had beans

-All bean seed is purchased, not from stock I saved

-Bed was not fertilized but treated with Azomite before planting at recommended level though it may not be as uniform as I would like.

-While I don't have a pH number, a soil sample did not bubble at ALL with vinegar and all my other beds are going gangbusters with other plants.

-No signs of insect infestation. This is organic. I do use NEEM (cold pressed oil) applied at dusk once a week, @1.5TBSP/gallon plus Dr Bronners @.5TBSP/gallon

I am thinking, does this look like a virus? If so do I pull everything or just let it finish out and not use that bed for awhile?. Today I did treat with epsom salts foliar @ 2tbsp / gallon because I have not much to lose but know that you can sometimes do more damage with "treatments" than not. The analysis of Azomite shows magnesium, and iron at close to 1% for each but only 0.02% for manganese which seems like a rather exotic deficiency.