This is a VERY common phenomena with phals - I have had many similar frustrations myself. They do much better going through the complete spike/flower phase in the same environment. Phals taken to my office in bloom do the same thing. If they start their spike/flower process in my office they go through the entire 3 month flowering sequence without a hitch. They are very sensitive to changes - cool drafts, hot stuffy rooms (a small fan with air movement helps), low humidity, etc.

It's always hard to diagnose what exactly is causing something to happen-- that's why doctors need so many tests to confirm or refute their suspicions.

I personally would depot and check the roots, especially on a newish plant. Some here think that's overkill, but it's fairly easy to slip it out of the pot. If it has big healthy roots, they grip the medium and there's no harm to the roots. You can usually just slip it back in its pot. If it's in unhealthy medium, you can repot in fresh medium.

IMO, checking the roots is like a doctor listening to your heart and lungs.

I always do that with a new plant, unless it has a huge blooming spike that would get bashed up. In which case I wait til the spike is getting ugly. This is because at least 1/4 or more of the new plants I've seen are in rotten old medium with fresh bark on top to freshen it up.

I keep both gel and liquid rooting hormone around all the time in case a plant needs a little help.

Since your spikes are yellowing, your flowers are essentially gone so you may as well check the overall health of the plant and repot into fresh medium if needed.

Your office may be too cold for a phal. 65F should be a minimum, not a max. This is especially true if it just has overall office lighting.

mayres, thank you so much for your input. I guess with purchasing a flower in-bloom/in-spike there isn't much you can do? I'll keep that in mind once some of my younger phals go into spike.

mehitabel, the plant at my office is still showing healthy blooms, it's just the buds that are yellowing and dropping. I will wait until the flowers are spent to re-pot unless the plant starts looking otherwise unhealthy. What rooting hormone do you recommend? Any opinions on the Shultz orchid potting mix?

I believe you may be right about the office temperature. I'm thinking I will just take this one home. What varieties might I look into that prefer lower temperatures and lower light? (I have a north-facing window, so I've been moving the plant up to the front office in the mornings.)

While examining the phal at home this morning, I saw a new bloom opening from one of the remaining buds! I've only lost one bud from it so far, so hopefully the new bloom is a good sign.

I don't believe you will find blooming orchids that prefer lower light than phals, or phals that prefer less than 65F.

Rooting hormone, I like the gels because they stick nicely. Clonex and Doc's are good. I'm sure there are others. For liquid rooting hormone, Dyna-Grow K-L-N, or liquid Hormex are good.

Your phal with new bud opening, may be ok. Losing just one bud is common as dirt. I misread your post to mean the whole spike was yellowing and many buds shriveling.

Once they are thru blooming, try to give them the best culture you can in order to give them strength to set new spikes in the fall. (see several orchid vendors and American Orchid Society culture sheets on websites for advice)

Thanks again, mehitabel. I will definitely get some rooting hormone for the next re-potting and will be using it on the bare root phals that I should be receiving shortly.

I will just take my office orchid home where it can enjoy more healthy lighting and temperatures.