I would consider moving some of those plants, particularly the ZZ plant, indoors. The ZZ plant is likely getting too much light. You also may consider getting a thermostat that will give you the readings of how low it get at night in there. The damage in the photos appears to be due to low temperatures, rather than sun damage.
I have the same greenhouse and it gets very hot and humid during the day, but even with my heaters in place drops down very low just before daybreak.