It is normal for old zucchini leaves to yellow up and die, but it doesn't seem like this is the problem your having. It's hard to say what's going on here, for sure you are having some kind of bug problem. What I'm not sure is if the bugs are causing the leaves to die or if it is a combination of bug and some kind of disease. Also how's the drainage in those tubs? If your zucchini are sitting in water constantly they will die. If it were me I would remove all the dead foilage, and throw it in a garbage bag. If there's any dead leaves on the ground pick them up also and throw them away. Then go to the store and buy some habernero peppers or any hot chiles. Pick up some garlic too. Cut up or mash up in a processor and throw the contents into an empty milk jug. Fill the milk jug with 10% skim milk and the rest water. Throw the cap on it and sit it outside and let it sit for a day. Then spray your leaves with this solution. This should help treat any fungal disease if there is any and also keep the pests away. You will have to re-apply when it rains or if you splash it off when watering.

That happened to me. While cucurbits are usually bred to have male flowers come out first (I'm assuming this attracts pollinators with the least expenditure of energy), I am told that for large scale farms, where I guess pollinators are used to coming, they are bred the opposite way. That's because they want their fruit fast, and if you have one male flower, you can do the job on many female flowers. So you may have gotten some of that latter variety.

I'm just trying to give them better choices for flowers, that's why I let the broccoli bolt, they'll go after it and leave the tomato blooms alone for now. I need to plant more pentas in the garden too, and make sure it's well enough away from the tomatos to not be affected when I spray the tomatoes. Squash is another story, hard to keep the bees away from it. If I see another die-off after using the spinosad I'll probably quit growing squash, and only grow greenhouse cucumbers inside the pool cage since a few moths will still get to them, but I can keep the bees out and still spray.... At any point the moths lay their eggs in the new buds of cukes/zukes and when the worms migrate down to the leaves they are so small you can't see them until they gain some size, so you can selectively just spray the BUDS every week and try to stay away from the flowers. Tom

If the leaves are only wilting during the day, it is likely they are just not heat tolerant as the plants that are not wilting. if they are small enough you could try a large row cover of bug screen while the sun is so hot. day wilt is perfectly normal. they should perk up fine at night and early in the day before the sun cooks out the moisture. my OG book recommends a bug screen FRC with pex tubing supports. Although this was recommended for protecting cold crops, not squash, so use your own judgement. the screen lets plenty of sunlight through, but not the burning heat that wilts the fragile plants. it would also cut down on the beetles. though fertilizing could be reduced, unless you keep plenty of openings for benificial polinators.