I'll spare you the trouble of wading through the thread; go to post #2596 (12/19/2017) to see the HC planting. It's 8 weeks old and has nearly 100% substrate coverage.
Your melting is probably due to the ferts misted during DSM. I did the same to some HC I had planted in a couple of terrariums; I drizzled some macro and micros and within a week there was melting and yellowing. It persisted for several weeks.
HC does surprisingly well with infrequent misting. I misted the terrariums every 2-3 weeks; sometimes more frequently. Lighting was provided by a SW facing window; not much direct lighting. Potting soil with no additional ferts added. I used the HC in the terrariums to supplement the replanting of the rescape done in December.