Thank you - It's really not good, I'm afraid. I've been having problems again. The plants went wild after filling with water, and I trimmed them the next week. After that, they turned brown and began disintegrating.
I assumed that the CO2 was too low, so doubled it. I'm injecting about 1.5b/s into the filter inlet now from 3 hours before lights on, and it seems to be dissolving for the most part. I've also increased the EI powders (KH2PO4, KNO3 and Trace) to a little more than the dose rate stated on the packs.
I've been fighting this for a while now, and 3 weeks or so ago I trimmed very harshly right back to the substrate. Some areas (actually those that get more natural light) are growing back. Other areas are still struggling badly, even with higher CO2 and ferts. Initial growth after trimming is fine, but anything below the tips soon turn brown and start withering.
The filter doesn't seem to be clogging or getting particularly dirty each week, and I'm doing 2x 50% water changes per week (was every day for the first few weeks).
Thoughts on problems:
CO2 - but I've already increased it.
Lighting(??) - I have an ONF Nano+ running at 70-80% for 6 hours. Plants with sunlight seem to do better, but I can't imagine I have a light shortage...
Ferts - powders don't go bad, right? I've had them (dry) for maybe 4 years.
Water - I can't get RO, but I could buy filtered water from the supermarket 5 litres at a time fairly inexpensively.
Distribution - Looks good to me, there seems to be a consistent flow around the tank - although the areas where the plants are doing better are possible lower-flow areas. High-flow areas are by no means extreme.
Any thoughts would be really appreciated. I've struggled with every setup since coming to Japan.