Recovering Zygopetalum

[shakkai]

A little while ago, I picked up a Zygo at a local garden centre. I bought it on sale because it had so many new growths showing - 6 already half way matured.

However, when I got it home, I found on repotting it that the roots to the old pseudobulbs were completely rotted. The new growths were (and still are) forming new roots like mad.

However, I am starting to think that this plant has had an overdose of nitrogen or something, as even though the new growths aren't mature yet, the buds for more new shoots are beginning to grow as well. The old pseudobulbs are completely wrinkled - they don't have any live roots to take up moisture, and they seem unable/unwilling to put down any new roots. All root growth is on the maturing pseudobulbs.

I have completely replaced the medium that they were growing in and divided the plant as some of the oldest pseudobulbs were beginning to rot, so I cut them out.

Is there anything else that I could do? Any recommendations?

PS. Though I say I think it might be too much nitrogen given to the plant at some point, it doesn't have any signs of over-fertilization (black leaf tips, etc.) - just hyperactive new grow.