due to close quarters and the close proximity of your bulbs, you can have a pretty decent difference in temp between directly at the tip of a specific plant and mid height on the walls. i would definitely check temps at the same height of your pitchers directly under each bulb. once you have a high/low temp differential in the different locations you can better decipher what's going on directly at the plants by your reading on the wall. for example... say there's an 14*F difference between where your meter is stationed and directly on the plant... and you have a significantly hot week or something... you'll know without a doubt to move that particular plant for that week. all things staying pretty equal, that temp differential should be pretty steady as well.
just a thought. something to consider, etc.