unhappy Java Fern
I have java fern in several tanks, all are different substrates, different fish, different lights. All are low tech, low-medium light. I let the plants do their thing, in this tank vallisneria went nuts since June. Nitrates are always in the 20-40 range, water is around pH 8 and on the harder side. Java fern never does well for me. Almost no new growth from the rhizome, very often holes in leaves appear after some time. In some tanks it makes babies, but they don't grow either, to no surprise. What is it missing most likely? Potassium?