A couple questions - 1. Is this the first time you are growing squash? If you've grown it before, did you have trouble before? 2. Do all your plants have it or just certain ones? 3. Check and see what the pattern of the yellowing is. Is it random and patchy, or are the veins staying green with yellowing in between (chlorosis)? 4. If the veins are green with yellow in between, is there browning on the edges of the leaves, or wilting? If the yellowing is in between the veins with the veins staying green (chlorosis), that can be caused by several things. Over-fertilization is one of them. (Do you have a reason to think you over-fertilized?) :) Iron deficiency can also cause it. Another possible cause is really high soil pH (alkaline soil). You don't say where you are - some areas have naturally alkaline soil because of lots of lime. A soil test is always a good idea, you can get it done at your country extension office. High alkalinity can keep plants from getting iron, so it's iron deficiency again in real terms. If it's low iron or alkaline soil, you can try some iron fertilizer. I have a patch of soil by limestone walls where lots of shrubs were chlorotic; last year I did a good application of iron fertilizer and they are growing great guns now with really good deep green growth. Good luck!

That could be one or several things. Perhaps water stress, excess bright light (could have been relatively brief, a day or so) and/or lack of fertilizer. It would help if we could see additional images. Useful would be the plant overall and perhaps one of the general area they are growing in.

Your tree is suffering from changing light conditions and also from transplant shock. I would ditch the Jobes in favor of perhaps Foliage Pro and Osmocote Plus, or Espoma Citrus Tone organic.

You could try and prune it to a smaller size maybe if you wish to keep it in a smaller pot, my key lime is quite small and it went through several flowering cycles this year. Citrus are heavy feeders so providing enough nutrients is key. I use granular citrus fertilizer on a monthly basis just topdress the soil, and when my plants are fruiting and flowering I use a water soluble fertilizer weekly. They also make water soluble citrus nutrients which can be diluted and sprayed on the leaves. I prefer to apply smaller amounts of nutrients more often. Also I recommend using organic fertilizer, non organic fertilizer will lead to salt build up in the pot. The picture is the kinds of fertilizer I use. In the background you can see some key limes in my fruit basket.