I have about five plants in my 20 gal and two of them in the back look as though they are going to die they have holes in the leaves, and some of the leaves are turning brown and the other plants are starting to show signs of a similar course just moving slower to it. I was wondering if there was anything Im doing wrong. they are in basic substrate of gravel about an 1.5 inches the light for them is a light specifically for plants and is 10,000k. I have started adding liquid plant food to try to help. any ideas would be appreciated.