What kind of substrate are you using? Someone said it is a heavy root feeder so I'm curious now if they're right. Also, what temp are you keeping it at? I may have to test the tempt theory out as well.
My temps are high in most of my tanks and it hasn't done anything but die back and cling to life.
To tell you the truth, my 10" blyxa cluster is floating. I shifted gravel here and there and I ended up taking about all the gravel from underneath. They have many white roots going into the gravel gripping. Even then, majority of the stems are in water and not gravel. I have 4 year old flourite and another random brand I picked up from petco many years ago. I EI dose and dose iron separate.
I saw a discussion about this a little while ago on the forum, it was said that water column dosing was the most essential vs all other. I know Im not being helpful but I cant remember much, all I know is EI dosing should solve everything related to plant food.
My water temps are all over the place, I took out my heater because I didnt have space. My tank is in the living room and the wind from my AC cools the tank. In the morning its pretty cool to the touch, I dont have a thermometer, but I have the sticker one outside on the tank glass. atm, at 11 pm, its reading 27c, which is quiet warm. I think thats the max my temps hit. My lights turn off at 8 pm. I have two T8 shop light right on my tank with a wooden hood, so it stays humid below the lights and water line and warms up the water. Ill check the temp tom morning if its really important to you. Although I question my sticker thermo. During late day its a degree or two warmer. During winters though our living room gets much warmer than during summer. So my tank temps are never stable.
I bought blyxa a year ago and they ended up dieing off. I later on read that they live in rice paddies and dont like water flow. Mine were in direct water flow so I thought that was the case. Currently, my big patch is partially in water flow, but so far so good.
Pic of my blyxa is in this thread (http://www.gtaaquaria.com/forum/showthread.php?t=47106