I started 4 Waltham butternut squash seeds, each in a coconut coir pod, a few weeks ago on a heat mat. They've been getting 300-500 PPFD of light 16 hours a day in a 21°C room and I was misting them twice a day to keep the coir moist. They were doing well until the first true leaves appeared, and now they're struggling.
I bumped them up a couple of days ago to 4" peat pots with seed starting mix, thinking maybe it was a lack of space or nutrients that was causing the yellowing of leaves. I continued misting them, but thought that maybe they were lacking in water because the pots are so much larger, so gave them a good watering instead.
Now they seem to be doing even worse, some of the yellow spots drying out and cracking. The second true leaves don't seem happy either.
What am I doing wrong? If it's overwatering, how do I know how much to water in these peat pots? The sides are dry.
Thank you!