A 40 Breeder tank is only 16 inches high. One T5HO bulb at the top of the tank gives you about 100 micromols of PAR, which, by itself, is high light. You use 4 bulbs. If you can turn off the two inside bulbs, keeping only the outer bulbs, then hang the light about 8-10 inches above the top of the tank, you should have plenty of light, and reasonably uniform light.
Right now, it is almost impossible to provide enough CO2 to keep all of the plants growing at the rate the light drives them to. The most aggressive growers will hog the CO2, as well as the other nutrients, leaving an inadequate amount for the other plants. Willow leaf Hygro is a very aggressive grower, but you may have an even better hog of CO2 in with it. So, I suspect the plants are just CO2 starved.
Also, as the plants grow bigger and more bushy, it becomes very hard to keep good water circulation in the tank. So, the Willow leaf Hygro may not be getting enough water flow through the plants to bring CO2 to them. Pruning them usually helps with that.
Right now, it is almost impossible to provide enough CO2 to keep all of the plants growing at the rate the light drives them to. The most aggressive growers will hog the CO2, as well as the other nutrients, leaving an inadequate amount for the other plants. Willow leaf Hygro is a very aggressive grower, but you may have an even better hog of CO2 in with it. So, I suspect the plants are just CO2 starved.
Also, as the plants grow bigger and more bushy, it becomes very hard to keep good water circulation in the tank. So, the Willow leaf Hygro may not be getting enough water flow through the plants to bring CO2 to them. Pruning them usually helps with that.
