Having boned up on online articles on how to grow kabocha (Japanese squash), I understand that it is not ideal to have them indoors and in planters. However, I live in a high-rise and there is nothing I can do to change that. I currently have four kabocha plants in two planters: one in a smaller pot and three others share a larger one. They enjoy the same soil (with a layer of compost) and consistent watering. All of them are about three to four weeks old.
A problem I am having is that the room is facing north, and though bright during the day there is nil direct light shining down on the plants. So I supplement (indirect) sunlight with six hours of LED plant lighting daily.
About a week ago one of the kabocha plants in the large planter started to show droopy signs: it now has two seed leaves and two "true" leaves. Its first true leaf just curled up one day out of the blue. Since the rest of its leaves were seemingly okay and the other seedlings also appeared fine, I didn't pay much attention. Today, another seedling in the same pot suddenly went down, limping on the edge. It was unexpected and had previously showed no sign whatsoever. The third plant, a recently repotted younger seedling, still seems fine. The fourth seedling, hogging its own planter, seems very healthy. This is really a headscratcher because I have made sure to water every day and not excessively (both planters have holes at the bottom to let out excessive water)
I fully understand none of the conditions are ideal, but what might have caused the two seedlings to go limp? Is there anything I can do to help them spring back? Should I worry about the other two?