Is This a Disease?! Help Needed!

[PalmTreeDude]

So one of my Washingtonia robusta started to go yellow and then the edges went brown and it slowly died. Then, two of my other Washingtonia have started to do the same thing a while back, but are still alive. Now, my final healthy one is starting to show the very beginning stages (slight yellowing in the oldest leaf). Then some of my Saw palmetto seedlings started to show "symptoms" and now it seems like my Archontophoenix cunninghamiana is showing it a little bit, although it fortunately doesn't seem to be progressing much. I can't tell if this is some sort of disease (I don't understand how potted palms indoors in Virginia would get a palm disease) or if they have some sort of fungus. Should I completely soak them in copper fungicide? I'm not going to lie, I am kind of freaking out a bit. Any advice would be helpful. I am not new to growing palms indoors during the winter and have been watering them each as I believe they should be watered while indoors (for example, Washingtonia get the least amount of water, to prevent rot). What could this be? Can I save these? I never had this problem before. 

[PalmTreeDude]

Slight yellowing on the healthy one. 

[PalmTreeDude]

The Archontophoenix. 

[PalmTreeDude]

One of the Saw palmettos. 

[Estlander]

1 hour ago, PalmTreeDude said:

So one of my Washingtonia robusta started to go yellow and then the edges went brown and it slowly died. Then, two of my other Washingtonia have started to do the same thing a while back, but are still alive. Now, my final healthy one is starting to show the very beginning stages (slight yellowing in the oldest leaf). Then some of my Saw palmetto seedlings started to show "symptoms" and now it seems like my Archontophoenix cunninghamiana is showing it a little bit, although it fortunately doesn't seem to be progressing much. I can't tell if this is some sort of disease (I don't understand how potted palms indoors in Virginia would get a palm disease) or if they have some sort of fungus. Should I completely soak them in copper fungicide? I'm not going to lie, I am kind of freaking out a bit. Any advice would be helpful. I am not new to growing palms indoors during the winter and have been watering them each as I believe they should be watered while indoors (for example, Washingtonia get the least amount of water, to prevent rot). What could this be? Can I save these? I never had this problem before. 

 

It’s certainly strange that so many very different species are having the same problem. 

Have you noticed any mildew or mold on the soil?  Wet soil indoors tends to get that. I think it’s a soil and being wet indoors kinda thing.
The reason I think that is that I have been into this ‘germinating and growing seedlings’ business for three years now and so far haven’t lost a single one yet.
Below is a pic of my current seedling collection.

I keep everything outside all year long and only bring mine in when we’re supposed to drop near freezing. After that back out they go again.

Since we get pretty regular rain here on the FL panhandle in the winter, then with the cooler temperatures and lower sun angle the soil never has time to dry out before we get another rain system. So far being wet and often also quite cool at night (40’s-50’s) hasn’t bothered my seedlings at all. 
Maybe taking them outside on warmer 50F+ days and letting the soil breathe might help and/or try changing your soil mixture.

Edited March 6, 2020 by Estlander

[Rickybobby]

I have 300 seedlings and washys are the only one for me that do this as well. Make sure you prettt much let the soil dry out between waterings. Also one thing I found is if I use my dehumidifier water. Which is acidic this seems to happen more as well. But as fast a frond yellows and dies a new one grows