Plants need 14 nutrients to grow, Nitrogen, Potassium, calcium, Magnesium, Phosphate, sulfur, Clorine, iron, manganese, boron, zinc, Molybdenum, nickel. If just one is missing or in short supply growth will be slow or stop and the plant could die. Light CO2 and fow will not cause leaves to die .
Some nutrients are immobile. Meaning the nutrients don't move within the plant. others are Mobil and can be removed from old leaves and moved to new leaves. The stripped old leaves then die and fall off. Based your description you have a mobil nutrient deficiency. If you look at the list of nutrients I wrote earlier all the mobil nutrient have a capital letter. My guess is that you have a magneisum and or a phosphate deficiency but I could be wrong. So you need to fertilize the water.
But please note that most fertilizers don't have calcium or magnesium or simply don't have enough of these for proper plant growth. The primary reason for this is that almost always tap water has more than enough. However if your water has a low GH level (general hardness) or you are using RO or distilled water you won't have enough. Consistent water changes like you are doing are generally necessary to keep GH stable in tanks. But if your water doesn't have calcium or magnesium you will need to use a GH booster to get enough for plants to grow. Increasing Gh by 2 degrees harness is typically more than enough for plants.
Some nutrients are immobile. Meaning the nutrients don't move within the plant. others are Mobil and can be removed from old leaves and moved to new leaves. The stripped old leaves then die and fall off. Based your description you have a mobil nutrient deficiency. If you look at the list of nutrients I wrote earlier all the mobil nutrient have a capital letter. My guess is that you have a magneisum and or a phosphate deficiency but I could be wrong. So you need to fertilize the water.
But please note that most fertilizers don't have calcium or magnesium or simply don't have enough of these for proper plant growth. The primary reason for this is that almost always tap water has more than enough. However if your water has a low GH level (general hardness) or you are using RO or distilled water you won't have enough. Consistent water changes like you are doing are generally necessary to keep GH stable in tanks. But if your water doesn't have calcium or magnesium you will need to use a GH booster to get enough for plants to grow. Increasing Gh by 2 degrees harness is typically more than enough for plants.