Repotting Neofinetia falcata

[MJSK]

Two years ago I read about the Neofinetia falcata in Orchid Digest and of course purchased one. A year later it grew 5 new growths and flowered. Of course this lead to new purchases, excited that I have the culture down and was going to expand my collection. I did not change anything, except to try to NOT to over water - I have lost many orchids to this problem. This Spring I lost two and the remaining ones developed several brown leaves and some black spots. Only one new growth on my older plant, which did not flower. I have seen a lot of root growth, though some is sluggish and some roots shriveled. I have trying to still not over water as we have a lot of humidity in Boston this Summer. We had a few weeks of humidity, overcast skys with a lot of rain. I have been letting the sphag moss dry out before watering again and trying to miss the new roots. I have recently introduced a KLN, Pro-Tekt, dynagro fertilizing regime,but have not seen much progress, though the plants don't appear to be worse. All the Neos are potted in the traditional way in the round pots with openings and in Sphag moss. The only thing I can think of is that perhaps they should have all been repotted. How often should repotting be done and is it too late in the season?