The  yellow and dark spots on the foliage suggests a leaf blight caused by rainy weather or poor draining soil. Too much water, or not enough drainage holes in a raised bed can encourage this fungal infection. Poke your finger into the soil and do not water until the top inch is dry. I am not sure where you live or what is in the soil of your raised bed but I do see blossoms on the plants so with warmer weather you could still have a vegetable harvest. In the fall I would add some organic matter to the soil to improve drainage in case the sand that you mention is clay soil that is impacting the drainage. If you do water the plants try not to get the foliage wet as this encourages more leaf blight. Finally, you can remove any leaf that is yellow to help stop the spread. Keep growing, Marianne Binetti