New growth and nodes dying, but fan leaves are fine

Id say root issues

 

@BrassNwood ull probably know alil better?

 

How are you treating these plants for spider mites. It looks almost like they were sprayed with a heavy dose of insecticide or perhaps it wasn't agitated when you were spraying it.

 

Does the soil smell anaerobic? Like rotten eggs. You stated they looked fine before you got them and only after you took possession of them did they begin to show issues. Are there any variables that have drastically changed. I've never used Lost coast therapy. So, I wouldn't feel comfortable commenting on that. I did however accidentally spray a clone with a bleach mix I use to sanitize my tent between grows and my plant looked very similar to yours. All the new growth was dead or dying the next day. The leaves died a few days later. The plant was dead within 5 days. I have since labeled all my common sprayers.

 

if they are in buckets, just drill a single hole in the side bottom and take a smell , the rotten egg smell is what i think you will find there ,

 

They looked like fabric pots from the picture @old shol4evr. That's why I didn't think root issues. Unless what looks like perlite on top of the soil is the only aeration that it had. Those pots are really hard to over water unless you run a really muddy soil. Or they were in a flooded plant saucer or tray.

 

thats why i asked, my daughter in law uses them bags, why i dont know, she will only water them about once a week in this hot texas sun right , now the root ball does twist up in there , she uses that kellog soil when she get the spring bug, i have taken those plants from the bags and they do twist up.
sitting in a tray ,maybe and probally , but even so the root system doesnt just stop at the bottom in them bags, anyway again my sugest ,hope the op figures it out , myself i wouldnt take that chance in my flower room , usually taking someone else plants has a reason , more often than not is because they already ran into problem and didnt want to deal with it

 

As hearty as I've found my plants to be, I would recommend completely repotting them - wash away all old soil and replace with your mix.

 

The only other time I've seen something like this was with a crab apple tree I had for years. Healthy as could be, then died very suddenly. It was wire worms that attacked the base of the trunk at the top of the root ball. They killed the tree within a few months.

 

With the whole plant affected it looks root related and like Tim suggested smell the soil. Dig a small hole and sniff the soil from the deepest part. The only time I had a plant look like that it soon was beyond saving and the soil stunk like rotten eggs (Sulfur) when I dumped it out.

The other possibilities are Root Aphids then fungal or pathogen.

BNW