I vote squash vine borers, too. Look along the first foot of the main vine for a small hole with what looks like wet sawdust nearby (borer poop). If you see that, it's a squash vine borer that's the culprit. It's probably too late to save your plant, but it's worth a shot to try since you'll also get some practice for next time. Slit the stem up from the hole longways until you find the borer & pull it out. Close the slit up as best as you can, then cover it with soil. Keep an eye on the rest of your squash & if you find another one & dig it out early enough, you might can save the plant.

For the most part, sprays are applied to prevent new infections on new tissues. Very few sprays kill existing infections The close-ups are so close up that it's difficult to know the plant's status. Some images appear to show powdery mildew while others show leaves with normal silver coloration. Here is a link that might be useful: your link made clickable

The Husband Guy says that it sounds like too much fertilizer. however, he also said that 3-4 hours of sun is not enough. If it got very hot where you are, a container pot could dry out very quickly. At any rate, I suspect that transplanting it did more harm than good. Sorry, but I think you need to forget this one and start over. He says that where you are, in South Florida, you would not have to worry about the last freeze date and could plant much earlier than March.

Hey Lana, your post just appeared today... odd. Sometimes those leaves will green-up, sometimes not. It just depends on how far gone they are. I'm not sure they will green-up 'before your eyes' lol, but results can be fast sometimes. I'm not familiar with that exact product but it should work well for a few feedings. The first number in the NPK percentage is 10... that's a little high for fruiting plants, but it's not a deal breaker. I would try to find another one with a lower N than the P and K and use the 2 fertilizers interchangeably depending on your needs at any given time. Usually companies offer products with different formulas, and if you have a preferred brand you can often get their fertilizers that are specifically for fruiting or flowering plants, and sometimes even geared towards specific plants like tomatoes. Early in their life, nearly all plants can benefit from a higher N. Nittrogen supports green, leafy growth. As a fruiting plant matures, it goes into flower and fruit (seed) production. It doesn't need to grow as much, so it's N requirements slow down. Some plants though, can use more than others, and leafy green plants like Kale, lettuce, spinach etc... are all about green growth. Even for them though, too much nitrogen can be over-kill and some say it can effect flavor. Like in most things, balance is the key. So, right now, and the near future, your zukes can use the higher N and that product looks fine. Read the label and see if it is a comprehensive - has a full spectrum of nutrients - including micro-nutrients. That soil you have sounds like it is soil-less (which is fine for containers) but it may not have a depth of minerals from which the plants can draw. It's very common to have to have a feeding regimen for container plants. Nitrogen is highly mobile in soil and mediums, so the frequent watering required for containers can wash it out. I think over-all your plants look fine. Over the winter, look into slow-release sources of nutrients. There are many choices and can depend on things like whether organic is a goal, ease of use, local availability etc... Give an update when you can, I hope this helps.