Hello Daniel,

This appears to be fungal in nature, potentially Alternaria or Colletotrichum. There also appears to be some stippling caused by a sucking insect, like a leafhopper, which could contribute to the yellowing of the leaves. There isn't a lot you can do for this season, but the removal of infected leaves from the field always helps to reduce the recurring incidence of disease in following years. If it's a small planting you could go in and remove any infected leaves and shoots to prevent the spread, but in a larger planting you may wish to wait until the off season.

If you're growing commercially I would encourage you to implement an IPM program, such as described in this guide from Missouri https://extension.missouri.edu/media/wysiwyg/Extensiondata/Pub/pdf/agguides/pests/ipm1037.pdf

If you're growing for yourself, I would look at the control options in that same guide and focus on early season insects and early season control of disease (some of the products listed are available to home growers). Typically earlier season control of disease prevents subsequent outbreaks later on in the season, though a wet season like this year allows for greater disease development regardless.