Used coffee grounds shouldn't be used raw in the garden. This is because the research is still out regarding using it as a topdressing. It inhibits some plants and helps others. It should be composted and that applied to the garden. Besides, there is little chance that you'll be able to supply enough nitrogen from coffee grounds to maintain plant nutrition.

Your container medium looks incredibly soggy. I don't think I can even see any perlite which leads me to believe you have a garden soil instead of a container soil. Cucumbers hate wet feet. You need to let the soil dry out quite a bit for the cucumber. It also looks like it has a nitrogen deficiency. You're not going to correct that with coffee grounds. They take too long to break down and won't give you much total nitrogen anyways. At this point you need a good water soluble fertilizer. You will also probably want to get a good controlled release fertilizer like osmocote. This will help provide nutrients over the long term. The reason the lower leaves are turning yellow and dying is because the plant is recycling the nitrogen in it in order to keep growing because it is starving to death.