Symptoms of nutrient surplus start as a hard black leaf tip die back - especially starting with newer growths first rather than the oldest growths. Also, Lance is right, excess phosphorous does make other nutrients unavailable. This is severly aggravated if you dry the plants out too much between waterings. Root tips also die, eventually root loss kills the plant. Symptoms are not terribly specific, but I did notice a pattern of loosing my most valuable plants (usually the salt sensitive species) after using 'blossom booster', I then had a long talk or two with Jan Szyren of MSU - Lansing, and I became convinced I had 2 problems - excess phosphorous and drying the plants too hard between watering. I switched to MSU 5 years ago and my plants are vastly improved. Read the literature, it is too lengthy a discussion for me to type here. But the best fertilizer regime for orchids is one that is frequent, dilute and high nitrogen, low phosphorous, high potassium and a goodly dose of Calcium, magnesium, & sulfur, and lesser amounts of copper, manganese, iron, and the rest of the micro-nutrients. Another key benefit of MSU formula is that Ca, Mg, & S are macro nutrients rather than micro-nutrients. I swear by the stuff.
.................. Candace - if you have been using MSU at 125 ppm, your problem is NOT excess phosphorous. If all your plants have been repotted since you switched to MSU you should not be having any toxicity issues due to nutrient excess. You did not mention how often you use the MSU, but 125 ppm N is at the low end of the dose range for continuous feeding, if you are not feeding this at every watering you may actually be starving you plants a bit. I would up you dose rate to about 200 ppm. N this might do you better.
Also sanderianum hate cool, they want Phal temps, and they don't want to dry out between waterings. Those are my thoughts
Leo