Sick Catt

[Lilac]

This is the yellow Cattleya I bought at the orchid fair last month. It's leaves were always rather pale but I attributed it to perhaps some sort of fertilizer or chemical they used to induce blooming in time for the fair.

When the blooms dropped I re-potted in bark. I noticed the leaves were still a very pale green, very yellowish. The roots were all brown and dark beige, but firm, and never got green upon watering.

I put it with the rest of the orchids and happily the leaves did become slightly darker green.

The other day I noticed the black area starting, and one leaf is turning yellow.

I took it out and saw there are no new roots starting.

I have put it in 'isolation sick bay' but is there anything else I can do for it?

Thank you in advance for your help.