You cannot harm plants with too much light. All the plants in your tank are found in lakes and pond wthat are blasted with full sun. On a clear day at noon light levels are about 20,000 lumens. Most rooms in homes are at about 1000 lumens. Heat is the primary killler of terrestrial plants. But in an aquarium your plants are surrounded by a vert effective coolant, WATER.
Other than heat the biggest cause of plant damage is a nutrient deficiency. Meaning of the 14 nutrients plant need to grow something is missing. Fertilizer could address that is the fertilizer has everything g your plants need. Many fertilizer don't have calcium and magnesium which are plant nutrients. The manufactures assume you have them in your tap water. If your water is soft you might be short on one of the two nutrients you could test this with a GH test kit or you could buy a GH booster. Increasing your water harness by 1 degree (Which is not a lot) would be snout to resolve a calcium or magnesium deficiency. Note the GH test kit tells you the overall level of Calcium and magnesium. But will not generate a number for just calcium or just magnesium . When most people have a GH issue it is typically one or the other but not both.
