[Avalon]

Nice tank MrJG! If I were you, I would double the trace and excel ferts. From there, I would dose KNO3 (powder). Purigen will remove your nitrogenous DOC's, misleading you (via your test kits) to believe you had enough N, but you will still need IO N (Inorganic Nitrogen) for your Ludwigia's. You might also consider additional Potassium dosing. Ludwigia's are heavy N feeders, and they will simply turn pale and dissolve when they don't have enough. If stems turn black, it's a lack of light, but when they simply dissolve, it's a lack of N.