PLEASE HELP!

[the loach]

I agree with Dougall they are probably not real Glossostigma elatinoides. Tropica is a very reputable nursery. They will have the ID right. Some guy from China selling seeds by mail... doubtful.
The emersed form does produce seeds though: https://www.nzpcn.org.nz/flora/species/glossostigma-elatinoides/

They say it is a difficult plant, so you really have to know if you have enough CO2 and nutrients in there before you can troubleshoot.

 

[Rainscapes]

I agree with Dougall they are probably not real Glossostigma elatinoides. Tropica is a very reputable nursery. They will have the ID right. Some guy from China selling seeds by mail... doubtful.
The emersed form does produce seeds though: https://www.nzpcn.org.nz/flora/species/glossostigma-elatinoides/

They say it is a difficult plant, so you really have to know if you have enough CO2 and nutrients in there before you can troubleshoot.

If this were true, why is the decay starting from one point and spreading, rather than sporadic throughout the tank?

 

[the loach]

For one, it could be genetics. Not all seeds are equally strong... I grow a lot of plants (non aquatic) from seeds, there are always some of them that are weaker/stronger as others.

Ps: I have no experience with this particular plant, but Tropica is a very reputable nursery. I have no doubt that it is a difficult plant if they say so (after all they sell them).

 

[Rainscapes]

I agree with Dougall they are probably not real Glossostigma elatinoides. Tropica is a very reputable nursery. They will have the ID right. Some guy from China selling seeds by mail... doubtful.
The emersed form does produce seeds though: https://www.nzpcn.org.nz/flora/species/glossostigma-elatinoides/

They say it is a difficult plant, so you really have to know if you have enough CO2 and nutrients in there before you can troubleshoot.

More importantly, can this issue spread to my stem plants?

 

[the loach]

If it is genetic, or a disease, no. If it is a deficiency because water parameters, possibly. It's not clear for me if it is some kind of algae or "in" the leaves? It has to be the real Glossostigma as well. If it is a terrestrial plant, it would be inevitable.

 

[Rainscapes]

I’m leaning more on parasite, or disease. Makes more sense to me that one seed was or became infected, and is spreading outward like COVID is. I’m super new to the hobby so I very well could be completely off on my logic. Can anyone recommend a tool that I can use to check all perimeters or separate tools? I need to start with the water quality as if this plant fails, I’ll need to know where I’m at in order to purchase another. Maybe some links to purchasing said tools? Thank you all again

 

[the loach]

Is it in the leaves or on the leaves (can your rub it off?) It's not a parasite. You need separate testkits for pH, KH, NO3, if you are really serious about it PO4 and FE. Are there no fish in there yet?

 

[Rainscapes]

Is it in the leaves or on the leaves (can your rub it off?) It's not a parasite. You need separate testkits for pH, KH, NO3, if you are really serious about it PO4 and FE. Are there no fish in there yet?

I have one mystery snail. That’s it. The tank was built with the intention of adding 15 oxodon paradoxus, which I can’t attain currently so I dropped a snail in there just for a little cleanup (not enough, I know). I do 30-50% water changes 1 a week. (The plan anyway. It’s day 6)

 

[Rainscapes]

Is it in the leaves or on the leaves (can your rub it off?) It's not a parasite. You need separate testkits for pH, KH, NO3, if you are really serious about it PO4 and FE. Are there no fish in there yet?

I believe it is on the leaves and then choking the plant and runs down the stem. I’m pulling some plants out that look like the stem and roots look ok, and others where the entire plant has blackened to the roots

 

[Rainscapes]

I have one mystery snail. That’s it. The tank was built with the intention of adding 15 oxodon paradoxus, which I can’t attain currently so I dropped a snail in there just for a little cleanup (not enough, I know). I do 30-50% water changes 1 a week. (The plan anyway. It’s day 6)

Here’s the update photo taken now. Affected area photo 1. Unaffected area photo 2. Day 6 under water.