...one plant is right amongst some branches, the other behind a large rock. This will manifest itself in co2 related deficiencies as the light from above will be equally as strong yet the plants won't have good access to the levels of carbon and other ferts that the rest of the plants in the tank do. The effects will be worsened with a plant that is greedy for co2.
As you can see the plant is not behind the rock. all 3 groups are very nearly together.