I planted a few summer squash seeds 3-4 weeks ago and they were growing great indoors under the lights. Just recently I noticed some of the leaves were turning brown at the edges. They are not brown spots, rather a uniform browning over the entire edge of several leaves. It seems to be working its way from the bottom up. The browning then works its way back to the stem. The brown area wilts and dies. I have attached a few pictures. I hope they help.