Originally Posted by MoneyMitch
what about the leaf die off?
The last thread we had on that, I determined it was the old growth, and if it continued then it would be a nutrient deficiency. The only other thing I can think of would be the high pH and hardness; E. bleheri is said to be good in harder water, but maybe your water is too hard. This has an effect on nutrients.
I'm not a botanist, and there is no quick answer, so I can only make some observations from my research.
An excess of some nutrients will cause a deficiency of another within the plant. If this is the case, then faster-growing plants will generally fare better because they use the nutrients faster, whereas slower-growing plants have to store them and there is a limit to this beyond which the plant suffers. An excess of iron shows up as dark brown spots or blotches, followed by yellowing of the leaf around these and then spreading. I can't see this in the first photograph, but it is a photo and this is still a possibility.
Chlorosis, or yellowing of leaf tissue, can occur when a plant is unable to produce normal amounts of chlorophyll due to a lack of nutrients. Pinpointing the specific nutrient is difficult, which is why I constantly recommend the comprehensive balanced fertilizers. I believe you earlier said you have root tabs, so one would assume this is not the problem. However, the hard water is obviously due to nutrients, calcium and magnesium and others. Perhaps there is iron in your water.
I am going to do some further research into this, hopefully I will find some better guidance to pass along. I can see other plants in the background, not clear though...are they OK or showing similar symptoms? Do you know the GH and KH of your water; the lfs may test it for you, or the local water supply might provide it. And your light, I thought you had a Life-Glo and a Power-Glo...or just the latter as mentioned earlier in this thread? Twelve hours of light is a lot, the Power-Glo is an intense tube and there could be an imbalance. Nutrients and light greater than CO2 from the fish...I would reduce the light period to 9 or 10 hours.