Agree.... too cold! Squash are the warmest of warm weather crops. If they are a month old and just getting second set of true leaves, they've been kind of stunted. A month in good conditions, they would be a lot further along.
I agree with sepeters. Just wait until your soil has warmed up over 70 degrees (soil temp is more important than air temp as long as not near freezing) and direct seed them in the ground. Squash are so fast growing that you don't gain a lot by starting them indoors anyway. If you plant them in the ground, when they sprout, they will automatically be adapted to the conditions.
Also you said potting soil/seed starting mix. They are different. Potting soil usually has fertilizer in it. Seed starting mix doesn't, has no nutrients. Once the seedlings have true leaves, they will start to fail in seed starting mix unless you are fertilizing. Leaves going white can be sunburn. If plants have been indoors, they are very tender and not used to direct sun, which is way more intense than indoor light. They need to be hardened off gradually.