Puzzled

This past Monday and Wednesday we checked our plants to find that both the temperature and the pH level were at normal as they have been for the past few weeks. To our surprise a bunch of the leaves were starting to wilt. This confused us because there was no change in anything except that we cut a few leaves off from harvesting a few weeks ago. We think maybe we harvested too late which effected the whole system but we aren’t sure. So we took off the wilting leaves and are hoping for the best next visit.