Sorry if this is not the correct forum for this, let me know if I need to post this somewhere else.
My pumpkin, squash, melon, zucchini and cucumber plants all seem to be turning yellow. Some are doing better than others, but none of them are the healthy green that I might have expected them to be. They are getting worse as time goes on, but I want to find out if this is fixable or if they are doomed. I live in Southern California and the temperature has been consistently in the 80s and 90s for a while now. The garden gets sun all day until about 4 or 5 in the evening when the trees give it some shade. Each of the plants are in beds which have some compost, manure, native soil and garden soil. The soil pH was about 6.5 when I put the beds together. I have been fertilizing them as directed on the fertilizer package, using Vigoro vegetable fertilizer.
At first I thought that the problem might be that I was over-watering, but after cutting back on watering and measuring the moisture levels daily to keep them from getting soggy, they still seem to be getting worse just as before. They are getting yellower, the vines are getting skinnier and the leaves are getting smaller. Their growth seems to be very slow. The yellowing begins at the stem and works its way out to the leaves until they are completely yellow and shriveled up. I recently added some Ironite fertilizer as well after reading online that this can help plants get back to a healthy green after over-watering, but it does not seem to be making a difference at all.
One of the plants does have a ton of tiny black bugs on the undersides of the leaves, but the rest of the plants do not seem to have any bugs so I don’t think that’s the problem, at least not for all of them.
If anyone knows how to stop this, please let me know. I had the same problem trying to grow pumpkins and squash last year - the plants would either die before producing fruit or would produce one puny fruit and then promptly die afterword. They never grew big vines the way that squash plants are supposed to, they would be very short and sparse and would never get much larger than what you might buy at a nursery to transplant. I wouldn't be surprised if this is a case of gardener-error as I am a complete novice at this and have yet to grow a very successful squash plant. Photos are attached. Thank you all in advance for any ideas.