Last week I reduced the temperature in my tanks, and the plants are growing better now, I think. I had all my heaters set too high. Since it's summer and we try not to use the AC more than we have to, I pulled the heater out of several tanks. I used the temperature table in Christel Kasselmann's book as a guide to optimal temperature. I looked up the fishes' temperature range online as well, but always erred on the side of the plants.