here is a good link for you from texas a m. it has a lot of pictures and causes of problems. look at the pics and see which one best fits you.

Here is a link that might be useful: cucurbit leaf disorder

Many thanks for the link, Steven. After taking a look at each of the photos, I'm simply not sure what matches. I was able to get some pictures of my cucumber leaves, so perhaps you or someone else can identify the issue? You'll notice that some of the leaves have a pale granular substance. This is garlic that adhered from a garlic/onion spray that used as a pesticide.

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looking at the middle leaf you can see in the back ground two other leafs. it has the appearance of target leaf spot. common on cucumber leaves. you need to start a fungacide regimen. copper fungacide or neem oil as long as the weather is not over 90. neem is an oil based fungacide and will scorch your plant. you can also us 3 tbs apple cider vinegar gallon water also. every spring i get the same thing but it slows down or almost stops when the weather gets hot.
next year try finding seeds that are resistant or at least tolerant of leaf spot.

happy gardening

i usually put a granular fertilizer down with all nutrients including micronutrients. emphasis on higher phosphorus and potassium content. like a 6-10-10, 11-15-11. you can put it down at anytime as a side dressing.

as long as you have not been feeding the plant high nitrogen it will bloom soon. just give it time. it took my plants two months to start blooms.

cucumbers will send out the main branch with male blooms then you will get side runners with female blooms. some people say if you cut off the first side runners it will produce more. i personally havnt tried it so i do not have experience. my wife likes pickles so i just plant a lot of plants and spend alot of time in the kitchen making pickles.

Just an update ... I used the apple cider vinegar mixed with water and it did the trick. New growth has come in healthy, vibrant and green. My cukes have finally started blossoming, so I am quite relieved!