Just a thought here, Since both varieties you are dealing with are man made variations, why not compare the slime coats of wild Discus to these man made ones? Maybe there is a difference in what they are passing on with the slime coat? Now that we have so many ways of recreating the natural water conditions of wild Discus, breeding them has become much easier than when I was doing it back in the 80s. I got them to breed but didn't have much success raising the fry. Jack Whattley was a regular supplier to the store I was working in at the time but he hadn't fully developed his special "fry food" yet so his methods were still "secret" so no help there.
lol I haven't been involved with Discus in over 15 years now so none of these new types were even around back then but I would think it would be interesting to know if the new fish secreted the same materials that the wild fish do and if not, what proteins or materials are different and so, is it the food or other means causing the change.
Just my 2 cents.