I have read that you are supposed to take temps with the thermometer not in direct light as it will give false high readings. I am confused because the plants are in direct light. What am I missing?
You are measuring two types of heat depending on whether you shade the thermometer or not. Ambient temperature and Radiant heat.
What you read is wrong, what you are thinking is right. Measure temps under the light at plant-top level, that is what the plants are experiencing so that is what you want to measure.