My Apple Cucumbers were doing well but now they don't look so good-- leaves turning yellow and dying, still in flower but no cucumbers yet. HELP. Not able to upload photo
Certified GKH Gardening Expert
Without seeing it, it will be very hard to say for sure.
There are many, many causes for this, depending on exactly how the damage appears. This can be due to over, or underwatering, Nutrient deficiencies, pH imbalances, fungal infections, and insect damage.
This article will offer some information on the proper care of cucumbers: https://www.gardeningknowhow.com/edible/vegetables/cucumber/tips-for-growing-cucumbers.htm