Miltoniopsis not growing. When should I worry?

[Kaykay]

As the title says, it's not showing any signs at all of new growth, and hasn't since I rescued it in July.

The history is: I got this NOID at a discount as had been left outside during the heatwave and was very burnt. Only one of the spikes survived the burn and went on to flower about a week later. All seemed to go well until the spike stopped flowering, then a fungus infection set in soon after. (It's now cleared up)

With all of that trauma, maybe I shouldn't be surprised that there has been no sign at all of growth, but now some of the leaves are starting to drop (looks like normal pbulb becoming backbulb to me) and I'm worried that with no growth I''ll end up with not too much orchid left for next year.

It's grown in an East facing LARGE window, in the cooler end of intermediate temp. I'm feeding once a fortnight with slightly weaker than directed 5.3-2.2-0.85 (seedling Brassia grown in same place has just finished putting out a new growth, is sprouting roots and generally happy, as is Vuyl. Cambria) Oh yes, I'm in London, England.

It's in a clear pot, and the roots are fine,but again, no growing tips, nor any sign of there having been any growth since I acquired it.

Any ideas? Or am I just suffering from Orchid-induced neurosis I do so love this little one, and want it to survive the winter!
thanks!
Kay