Tough week trying to figure out what was up. Had to work on getting the humidity under control and the ventilation right. Big improvement when I did. Plants look like they had slightly wet feet that needed drying out. Let them all dry out properly and then gave them 2 litres of water each. Installed a fan and some ducting for ventilation, which works well but now the humidity is difficult to control. Added wet towels to the tent, and started spraying the walls to bring the humidity up.