Excess CO2 or iron causing brown leaves?
I recently added DIY CO2 to my 75 gallon aquarium, and at the same time, I also added extra iron (seachem) and seachem substrate tabs. Because of the increased CO2, I also increased the photoperiod. Quite rapidly, some of the plant species started showing brown leaves (including dying brown parts around leaf edge), especially Crypt lutea. My downoi has a bronze/dark color to many leaves now. Could this be caused by too much light (9 hours), or overfertilization or too much CO2? Previously, I had just been dosing with flourish comprehensive and trace. CO2 levels seem to be at least 30 ppm based on ph and Kh measurements. pH went from 7.6 to 6.8 after adding the DIY CO2.