I have had this tank for about 8 months now, and my plants had been growing fairly slowly. I didn't want to heavily plant the tank as I do have a small pleco in there currently and he tends to knock around plants if they're too close together. Anyway, for about 2-3 months, what I assume to be anubias plants had developed these dark spots on their leaves. other plants in the tank began to show leaf decay as well. I picked up some generic Aqueon Aquarium Plant Food. That worked for a while and the dark spots on the plants began to fade, except I had to use well over the recommended dose for this to occur. I quickly ran out of fertilizer and decided to switch to Thrive+. I have been using it for about 2 weeks now and there has been no improvement, is this normal or am I doing something else wrong. The tank is set on a timer to have 11 hours of light daily.