Is it gonna die?

[LittleBigOwl]

Hello to everyone! Here is my Grammatophyllum, very sad one. So the short story - i got in back in may, big division (how it was advertised). Repoted it right away from bark to a mixture of lava rocks and sphagnum and everything was fine for three months and than as soon as new growths matured something went wrong. Leaves all turned brown (first ones were on new growths in the middle) and died off. Today unpoted it, cleaned all roots (some looked dry, other looked rotted, probably the oldest one) and here is what i have left with. A lot of new growths (one of the new one just fell off), no new roots and it feels like roots are growing couple of inches and then stop. So question is - how to save? I have all same issues with grammatophyllum, grammatocymbidium, cymbidiums and most of oncidiums. But oncidiums are in pure sphagnum now and indoor. So looking for any help.