It is not unusual for the lower leave to yellow and die.

But I also see other leaves that are also pale green. To me, they need a doze of all purpose fertilizer.

Another thing about trelissing cucumbers is that they get sun scalds and wear out faster. By trelissing the sun exposure is increased dramatically. Tomato leaves and vines are very delicate.

Final Comment:
I will trim ALL the the dead and yellow leaves. They have absolutely no benefit and can harbor diseases.

Ok great. Thanks for the great feedback. Do I cut the leaves or the stem too? Also what kind of fertilizer??

One more question. Whenever I go into my veg garden I seem to get itchy rashes on my legs and arms!! Does this happen to anyone els? What is it??

Are you getting skitter bit? Cut the dead or dying leaves. Make you a compost tea. If you dont have your own compost just get a good grade of compost from a garden center and use that. A liter of compost in a 5 gallon bucket with 3 oz of mollases and water . Give it a stir and let it sit over night. An aireator would be nice but not nescessary. Then water carefully. You will get the nutes you need and some beneficial microbes as well.

There is a post about getting a rash from squash. Give it a look! NT

I know every time I work in the garden I stink. My DW says "you smell like the outside."
Sometimes I don't even sweat, I'm just harvesting a few tomatoes, and I still end up with the outside/garden smell.

Smell, pleasant or offensive is a subjective thing
A lot of people love the small of tomato leaves. I do not care one way or the other.