Hi, 

What you are describing may well be a pollination issue. Cucumbers have separate male and females flowers instead of having one flower with both parts adjacent.  When initially flowering, male flowers seem to be the ones that are first produced in abundance, so pollinators might visit but there's no female flowers for bees to pollinate yet. Also., pollinators are influenced by weather--too rainy, too hot and there will be fewer trips by bees to the open flowers. Also rain can wash away  and  also degrade pollen, If you have female flowers that aren't adequately pollinated, they will just drop.

High heat also affects pollen viability and can make it too clumpy/sticky for bees which aren't as active in hot, humid conditions  of they type we have been experiencing.  When pollination is inadequate the fruits that form can shrivel and be aborted.

Once we get out of this recurrent weather pattern, the cucumbers ought to recover as far as producing fruits goes. 

If necessary, you can also start new cukes right now (mid-July in central MD ) to replace those you have-- if there are other issues aside fruit pollination.