Ewww, my god....what you need to do there is completely repot the orchid into some Radiata (or Fir) bark. Also give it a good dosing of Sulphur or Potash when you do. That looks sick I personally would pot into Terracotta, as it breathes for the plants roots, as they prefer a lot of air movement around their roots. When you do repot, trim off all of the dead/dying roots, to minimize infection, then treat with sulphur or potash to help control any existing infections. It also looks like you might be watering it too much, try reducing watering, so it has a dry period of about a week. They like to dry nearly completely between watering. I would also reduce feeding, if you are using your fertiliser at full strength, this will be causing a few issues, especially if it is organically based (bacteria love it lol). Reduce feeding to fortnightly, and half the manufacturers directions. Probably doesnt need to be that warm either, but then a little warmth never hurt any cattleyas The warmer temps have most probably influenced the production of two new, healthy growths i see there. This is actually a perfect time to repot when the growths are only little, as the new roots will settle in nicely!
Infact, just re reading your post, the lack of healthy root mass probably is the cause of your shrivelled pseudobulbs, as there isnt enough water being taken up by the plant at watering times.
Hope it helps!