Dendrobium Proud Appeal brown leaf patches

[jmforan]

Had for almost 2 years, has not bloomed since I bought it (when it had 10 spikes!). Leaves have been turning brown for several weeks, a few at a time. No evidence of any scale or infestation to my eye. Roots were not in good shape as you can see. Any help? Live in Greenhouse in Southern California, never below 60 or above 86 F. 50-60% humid. Water 2 x week, fertilize weekly weakly. Thank you!