This plant is crying for some fertilizer and water. You may not water it enough.

Hey YellowThumb, do you think that's what it is? Its really hard for me not to over-water so I usually water my plants twice a week but this cucumber always seems to be on the drier side (even though my moisture meter reads "moist"). I'll try to water this plant at least every other day to see if that helps.

Thanks for the response!

Yellowthumb, I think this plant is over-watered. I've seen gnats around the soil which makes me think there is something wrong with soil and possibly roots. The leaves are getting paler yellow by the day. I cut off the cucumber and wilted leaves. May try to get it some iron or something to turn it back green but if its root rot, may just have to dump the entire plant. :(

How warm is your weather? If it's hot. Cucumber can drink lots of water.

The plants lost all their lower leaves. That's the reason I am thinking underwatering, or the pot is just too small. Have you fertilized it recently?

I'm in San Diego, CA (coastal) so its usually always in the mid-70's. Although last week it did get in "scorching" 80's. Not sure if that's too hot for it. Today its 73 degrees F.

Most of the lower leaves are gone because I cut them off as soon as they start to yellow, wilt then die. It started with the lower leaves and have moved up the entire plant. Its a lot more pale yellow now than it was a week ago (when I took the photos). Maybe another sign of root issues?

It's in one of the larger clay pots. Maybe 12 gallons? I don't know for sure but I don't think the pot is too small. I have larger plants that are in smaller pots that seem to be thriving.

I fertilized again about 2 weeks ago (with one of those slow release fertilizer sticks).