Discus White Spot?

My large discus has white fluffy spots and is a little out of sorts. Still eating. I dropped the temp a couple of days ago to 25-26C as I had 5 neon cardinals die and thought it was the temp. I have attached pictures. 
 
I have turn the temp up and put one treatment of Myxazin into the tank. He is in there with a bunch of other fish. Gourami, Platys and angelfish. 
 
Any advice appreciated.

Size of tank? Water stats please?

Tank mates too.

Discus are quite high on the care level and should really only be kept in tanks by themself, at least a 55 gal tank for them too.

Ph 6.4 always steady Ammonia 0 temp now 27C
2 Gourami 2 Angelfish 2 Discus 3 Platys
100 litre tank
Discus have never had a problem until now

Does look like white spot.
 
I have to agree that the stability that discus like (not to mention that they're actually quite large fish) does mean that they need something bigger than 100l.
 
I don't agree that they need to be on their own, just that you need to be careful with the stocking as they like their conditions to be different to many others that we like to keep. Putting them in with angelfish isn't actually that unusual.
 
I suspect that the undetectable toxins are your problem with the tank size, although well done for keeping the stats good otherwise. It might be that they've all simply grown to the point where the tank can't sustain them long term.
 
As for the ich, especially given my concern about the cause, plenty of clean water, big water change to get the conditions perfect, then add in your treatments and turn the temperature up. Ich cycles faster in warm water and the medications only work in the free swimming stage. Make sure you have no carbon or equivalent in your filter as well.
 
Longer term you're going to have to look at a larger tank I'm afraid, but that's for after this unless you have the resource to start it up now and you can use this tank as a hospital tank for the badly affected ones.

Thank you so much.. Fingers crossed. 
 
It would be a pity to lose him, they all get along so well... even when angel's laid eggs there was no turf war. 

That doesn't look like white spot to me... I've dealt with white spot plenty of times and that isn't white spot.
 
My boyfriend(darksoul996 on here) says it's something discus get when unhappy. They go white(like above, it looks more like he's losing his slime coat), then they get fungus and then they go downhill really quickly and most likely never recover unfortunately. Which means, if it is that - Your discus is unhappy... What are the dimensions of your tank? If it's 100l is is 36x12x12in?

Yes white spot from my experience is more tiny grain of rice size.. every where in the late stages. When you describe it as "fluffy" it does bring other things to mind such as a fungal infection.
 
Try and get your water stats to us - Ammonia, Nitrite, Nitrate. How often do you water change?
 
Myxazin is a good treatment for fungal/bacterial infections.
If it was white spot you'd need to use Protozin.
 
Would you be able to post some more pictures?

More pics.. he is more sluggish today. hanging at the top of the tank