[Zapins]

Garrett, these symptoms are quite typical of nitrogen deficiency. Steadily smaller growth along with deteriorating older leaves (which I can't see in the photos you posted above but are probably there further down the stems of stunted plants). The low nitrate readings are also probably indicative of nitrogen deficiency.

Look over Rotala macrandra during a nitrogen deficiency for a comparison:
http://deficiencyfinder.com/?page_id=620

• Are any other plants showing these signs?

• Can you take photos of them?

• Are older leaves deteriorating?

To answer your questions: plants will use Ca and Mg over time, which will decrease the GH. This does not happen very quickly and should not cause a problem if you do water changes. 16 dhk and my KH 6 dhk is not too high for plants if there is roughly equal Ca and Mg or more Ca and Mg, however, it is possible to cause problems if your GH is totally made up of Mg because of your dosing, so just be aware of that.

 

[Zapins]

Would you mind taking photos of your plants? New and old growth of as many of them as you can manage. If we are able to confirm nitrogen deficiency then I'd like to add the photos to the deficiency finder with your permission.

As for the calcium, you don't need to be too specific about ratios, just make sure the calcium is = to or more than the magnesium for a problem free experience. You can use the fertilator on APC or wet's other calculator to figure out teaspoons/tablespoons. Also, a good quality digital scale can be bought on ebay for about $10-20 shipped, so you might want to consider that in the future. Spoons are difficult to work with because you have to constantly deal with fractions, estimate the grams, then calculate out ppm values instead of directly using a known gram amount for ppm values.

The first thing to do is to not change anything with the Mg/Ca at the moment, fix the nitrogen issue, then once we confirm that is causing the problem then we can fix the GH. If you change two things at once you won't know for the future which caused the problems or how to specifically correct it.

 

[Zapins]

Thanks for the extra pictures.

I'm finding it difficult to make out for certain but are the old leaves (the mottled looking ones) actually damaged or is that algae on them?

 

[Zapins]

Thanks for the clarification. I'm looking forwards to the next update to see if the nitrates you added solve the funky new growth. If they do then this problem is likely nitrate deficiency and I can add it to the deficiency finder. I don't have any nitrate deficiency Ludwigia entries yet

Any more close up photos would be helpful if you'd like to take more pictures for the database.

The new growth should start growing normally within a few days. Probably 3-5 days you'll see healthy looking growth coming off the plants and within a week or two the plant will have several nice healthy leaves.