Epicattleya Rene Marquis Tyler - progressive leaf yellowing & Drop

[Skippersmom]

Good morning wise ones. I need some advice on 2 Epicattleya Rene Marquis Tyler orchids.
Unfortunately the system dumped my first detailed explanation, so I will endeavor to cover my question with more brevity. I apologize for any omitted information and fire away with your ?s as needed.

I am mostly a beginner. Have been doing orchids for about 8 years, mostly Catts, Phals, Catas and a few Vandas. Have even rescued a few plants from others.

I thought I did my homework on these Epicat. Rene Marquis. Watched videos and did on-line research. Orchid Society handout indicated that they were not fussy about the type of water. I do check pH on my source periodically and checks out.

Little Guy - there WERE 2 pots of this purchased from a northwest U.S. source, approximately Febr. 2022. Static and even putting o leaves for a bit. Then 1 began slowly dying. From bottom up, leaves would shrivel a little, then yellow, then drop. It was finally totally dead. So I repotted Little Guy #2, fresh cattleya type media (from a good source I’ve used for years) with a skosh of sphagnum moss to help hold a little moisture (winter indoors I cannot keep the humidity up around the group, so all my orchids have varied amounts of moss,). Cleaned roots, treated top to bottom for fungus. Sits in a south window at my sink. Keeping a close eye on it. It seemed to be great for about 6 weeks, then then bottom up failure started.
Big Guy – stoked by my ‘apparent’ rescue of Little Guy, I boldly purchased Big Guy, hoping that a better established plant would do better. This was about a month ago. Quarantined in a different room, treated for fungus, etc….the unprosperous look started nearly immediately. I have had it for about 4 weeks and it is dying SO FAST.
Pests = checked for mites & pests, cannot find any.
Fungus = Retreated for fungus (Cosan).
Fertilizer = ‘Little Guy’ has Osmocote Pro mixed lightly in the medium.
……………….’Big Guy’ has a grey particle slo-release on it
Big Guy has 2 healthy stems still attached. I want to be proactive and any intervention that I can do to at least save those, I want to try. I could pull it out of it’s medium and repot, but that wasn’t the perfect answer for ‘Little Guy’ so before I do anything major, I seek guidance.
I am feeling like the Grim Reaper!!!
Thank you in advance for your thoughts and assistance.
SkippersMom