I am afraid it might be the start of the dreaded new, virulent southern strain of Downy Mildew, which hit hard in the midwest the past few years. I heard that it was brought up by hurricane remnants in 2005 as spores, but I suspect this is mostly urban legend. However it got here, it's bad news, as it seems to be fatal to most cucumbers and melons, and it also attacks squash and pumpkins, but they seem to tolerate it.

The key to control is repeated and frequent fungicide applications, and rotation of products to avoid resistance. But, this is hard to do for a homeowner.

Michigan State University Cooperative Extension has a lot of information about Downy Mildew -- look under the Vegetables tab.

Downy mildew tends to hit you later in the season, though. Let's not rule out insect damage here. I would suggest rising early tomorrow morning and go out to the cucumbers at daybreak and check for any cucmber beetle activity. They chew on all parts of the plant injecting a virus that makes the plant turn brown and crispy over time, and ultimately leads to plant death. I am a little south of you here in 6b and I have the beetles right now, so they may be arriving where you are.

denninmi, thanks for the reply. I'm not so sure if it is downy mildew, because there is not really anything on the backside of the leaves. Though I won't rule it out yet. Any suggestions on a spray? Does neem oil really work on this?

raisemybeds, I haven't seen any bugs on them, but I haven't checked first thing in the morning yet. After researching last autumn, It does seem like this is what got my plants last year. I top watered last year too, which I believe helped spread it. Got soaker hose laid this year. But it's been constantly wet almost every day this week.

I found what appears to be flea beetles on the leaves this morning. Could this be what is causing this? The flea beetles have been on my potatoes, but don't do enough harm to really cause any concern. I sprayed with neem once, but was not really worried about it.

But could they do this kind of damage to the cucumbers, or would I be wrong to blame this on them when the reason could be a disease or something?