Brassavola seedling leaves got blackish lines along midrib

[sweta]

Thank you for the response. This seedling came in sphag moss so I thought of not changing the media drastically since its a seedling..so I added some bark but has more of sphagnum moss. After seeing your post I removed the sphagnum moss. I find it a challenge to keep up with watering in dry home temperatures. You are right that the roots have been in wet soggy sphagnum moss. In addition the warmth from the grow lights might have cause some kind of infection. Can I use physan instead of copper fungicide. Btw I use rain water with repotme fertilizer.