Not too long ago the leaves were massive & looked healthy and encompassed the entire bed. Now, I'm seeing some yellow/brown to the leaves and some of the leaves have even completely died and are now shriveled and brown What could the issue be? Should I be adding something (compost, fertilizer, etc...)? Are they overwatered? Under? IDK!

I see some leaf-burn there, as well. According to a current discussion in the question forum, the most obvious probabilities are potassium deficiency or over-fertilizing. Over-watering and soil acidity are also possible causes.

The soil looks very dry. Are they in pots? What kind of soil are they in? Are you fertilizing? Potted crops need regular feeding and squash especially are heavy feeders, plus they use a lot of water.

NewGardener95 said:Not too long ago the leaves were massive & looked healthy and encompassed the entire bed. Now, I'm seeing some yellow/brown to the leaves and some of the leaves have even completely died and are now shriveled and brown What could the issue be? Should I be adding something (compost, fertilizer, etc...)? Are they overwatered? Under? IDK!

From what I understand, you've grown these successfully to this mature stage.

I would first look at whether I had changed anything in my care for them. Did I add some of the new "Doctor Whizbang's Miracle Beaver" fertilizer? Did I accidentally grab the concrete cleaner rather than the fish emulsion? Just basic things.

Then look at possibly environmental changes...whether getting hotter?...rain less in frequent...more frequent? Did you adjust your watering routine to the rainy spell or drought? Stick your hand down into the soil and see what it feels like, or if you've got a probe moisture meter use it.

And then you have the aspect of disease and insects which is a wide open area.

Looking at your pictures the green leaves look pretty healthy. Though, on image #1 I do see some slight yellow mottling (and it is slight) that could be signs of early downy mildew. But, with the dead and yellow leaves I would think there would be more green leaves with yellow spotting on them if mildew was the issue.

Seeing the collapsing green leaves leads me to believe you may be having problems with squash vine borers (SVB). The moths will lay their eggs on the vines or leaves usually closer to the crown/base of the plant where the fruit grows. The eggs hatch and borers (grubs) will drill into the vines to feed and grow...efficiently cutting off the water/nutrient flow to the leaves...basically a big plug in the hollow center of the leaf. Seeing a healthy green leaf that has suddenly collapsed into a wilted heap is usually a strong signal that SVB have infected the plants. One day the plant can "look" perfect and the next day it looks like it has been deflated. They are difficult to deal with. The best practice, it seems, is to find out when the moths "come out" and plant so the plants will not be mature at the same time. I'd check with some local growers in your area if you know some other gardeners...or if you happen to see a nice garden beside someone's house stop and inquire...gardeners *do* like to talk.

There's other diseases, other bugs, etc.,. I'm just a newbie and these were some things that came to mind first.

Best wishes!!!

@Serpent What could I add in the case of potassium deficiency?

@NMoasis Yes, in pots! I created my own soil mixture of topsoil/compost- everything else that's growing in this mixture is doing great but my squash isn't thriving like the rest of my veggies are. I've been watering more frequently (plus we've had 2 days of non-stop heavy rain in Houston so hopefully that'll do them good).

Oops, I actually am not fertilizing....what kind of fertilizer do you recommend?

@Intheswamp thanks for the input! I actually did have some changes. the weather started getting hotter in the area plus it was raining less frequently so I was watering by hand so I'm thinking maybe I just wasn't watering thoroughly enough!

You have options, granular or liquid. One that is formulated for fruiting crops like tomatoes will be fine. It will have a slightly lower nitrogen percentage (than one for leafy greens, for instance). Whatever form you use, apply at about half the recommended strength for in-ground plants.

NewGardener95 said:@Intheswamp thanks for the input! I actually did have some changes. the weather started getting hotter in the area plus it was raining less frequently so I was watering by hand so I'm thinking maybe I just wasn't watering thoroughly enough!

Yeah, they gotta have water. Water'em till water runs out the bottom of the container. Wait a few minutes and then water them some more. You want to get the soil good and soaked. Then check every few days and water when the top one or two inches are mostly dry. Don't let them get too dry. I usually like to see water drain from any container I water, but...I don't grow much of anything in containers other than seedlings.

@NMoasis got it thanks and is it safe to fertilize if the squash has already started to grow?

Yes. If you're using 1/2 strength liquid, try every two weeks. If you're using granular, follow product instructions for frequency.

Please know this is an approximation. Every plant and every soil behaves differently. My sense is that your plants need a boost. See how they respond about 5-7 days after fertilizing. If they start looking better, that was probably the problem. If at two weeks there is no improvement, then it's something else and don't add more fertilizer at that point.