The young leaves look good. Probably needs more nutrients but I'm no expert on what. I had squash plants that looked like that last year and I added bird poop to the soil. The following week the leaves turned a nice dark green.

Hi, I see this post is from last month so I may be too late. I had a similar problem and it turned out they were lacking nitrogen. You could try a fertilizer high in nitrogen or fish emulsion or worm castings depending on your preference. Once they start flowering and fruiting though you'll probably want to switch to something lower in nitrogen. Hope it helps!!