Leafy green problem
Something is attacking chard, beets, & kale. I see no bugs each time I search? Help! Does this look bacterial? Fungal?
On the cucumber: Yellow Spots on Leaves—Pseudomonas syringae: Cucumbers often develop yellow spots on the leaves. These are caused by the bacterium Pseudomonas syringae. They have little effect on yield, but they make the leaves unattractive. These bacteria spread on wet leaves, especially when the wet leaves are handled. Avoid overhead watering or working in the garden after watering or rain to reduce incidence and spread.
It looks as though your beets have a fungal disease called Verticillium wilt. Verticillium wilt attack the roots of the beets and causes the leaves to turn brown and wilt. You will need to treat the entire plant with a fungicide that can be bought at a local garden center or nursery. Other remedies includes: insuring good air circulation around and between the beets; watering around the base of the plant instead of the leaves; remove fallen leaves of infected plants; inspect plants regularly.
For pests, such as on your Kale leaf, treat the plants with Neem Oil.