A few leaves on the oldes pbs could yellow normally. But the yellowing shouldn't continue and continue. My guess would be dying roots. This could have begun before you even bought the plants, and is really quite a common thing in new plants that were heaven knows where before you got them, so don't get on a guilt trip. Focus on restoring the plant's vitality, which you can fairly easily do if they aren't too far gone. When roots are compromised, plants start to discard leaves. My advice would be to stop trying to get more blooms. You won't get them on an ailing plant. Also, many oncids bloom twice a year, but others only bloom once, so you can't expect new blooms til at least next summer, maybe next fall. Concentrate on restoring the plants to health, and they'll bloom for you, probably next fall. I would take them out of the pot and examine the roots. If the roots are good, make sure the pot isn't too big for the rootball, and that the drainage is good. Also make sure you do not plant it too deep-- *all* of the pbs should ride just on top of the medium, not *in* it. If the roots are bad, oncids re-root quite well in a clay pot with a little lava rock on the bottom, and then a thin layer of sphag over the lava rock. Water when the sphag is crispy. This creates a nice humid atmosphere around the the plant, and fosters new roots. New roots form only on the newest pbs, so I would also put rooting hormone on the newest pbs, at the bottom of the curve on the pb, where roots will appear. Give them the best light you have. With rooting hormone, it can take as little as a month for new roots to appear. Expect some action from them as the days get longer and the sun gets stronger. Don't fertilize until the plants have roots again. Good luck.

they are phal orchids, about every other night i leave the stove light on for them, its been kindof cloudy during the day, so i think that their getting less light than usual. i moved the big one from CO here in August and it did well, its got a lot of sentimental value, as its my first orchid, and myhusband bought it for me the day our first daughter was born, and since hes deploying in Feb, i would be crushed if it were to die! the leaves that i didnt cut are healthy and leathery, um...ive got them planted in basically terra cotta pots with a drainage hole in the bottom, and their planted in schultz orchid mulch, its a combo of bark, charchol, and ceramic pebbley chunks. i water the plants about once a week in my sink, i fill the sink up to the brim of the smallest pot, and soak for about 30 min-a couple hours, drain and put them back by the window, and i use the schultz orchid fertilizer about once every month or two. theyve been doing fabulous until now. is it normal for orchid leaves to die, or is that mainly just the flower?

Thanks for the reply. It does look like a calcium or magnesium deficiency, which if it is, is not likely due to lack of the nutrients but an uptake issue as you said (I use epsom salts foliar and bone meal in the soil). Does epsom salt increase soil salinity over time? The location is near the ocean and salt build up is a concern. Also, can high soil salinity effect nutrient uptake, like a mineral or ph level imbalance can? I don't believe it is a calcium deficiency though because I am not experiencing BER. The bottom (flower end) is not soft/mushy/rotten but tough and scarred like in the pictures above. Thrips and some spider mite damage may be at play, but again this seems unlike to be the problem since only new leaf growth is effected (maybe I'm wrong here, perhaps the pest are only attacking the young shoots first). It seems the most important, stand alone issue is trying to understand what is causing those dead ends and flowers to fall off, this is an issue I am having trouble explaining with any of the pest or nutrient issues we just discussed. Thanks for the input! I still haven't figured it out and need all the help i can get

Stu, it is likely due to some sort of insect based on what you posted. I would treat with neem oil or a 3 in 1 type product. Others who have the time spray the whole tree down several times a day for a week with water to knock off the insects and eggs.