Beginner Gardening: Squash plants are dying. How to save them?, 1 by Silvermist

Silvermist wrote:
It all started when: I put my mini squash plants into larger containers and added fertilizer.

I tried hardening them off for transplant and laid them out in the sun the next day but then noticed that one plant started to get brown spots on the leaves and soon enough shriveled and died. This started a trend. Soon each of my summer squash plants started to yellow and brown one by one. Why did they start dying? Did the fertilizer stress them? Too much sun exposure stress them? Is it transplant shock? Drastic temperature changes from indoor and outdoor exposures?

Any advice or tip is appreciated.