Yellowing Dendrobium

[Evangeline Bourne]

Hi guys,
Things have been a bit quiet for me for a while. my plants have been happy and healthy and growing vigorously, which is always a good thing.
Now... It was my husbands birthday a couple of weeks ago, so of course, I got him an orchid, as all good wives of orchid geeks are wont to do. :P his sister also got him one, and he got 3 for himself as an extra gift LOL. so we are enjoying 5 beautiful blooming plants. 3 dens and 2 vandas.
they seem to be doing fairly well, but one of them has started yellowing... the leaves and also the stem part, which is kind of worrying...
I will take some photos in the morning as its too dark to get any pics that will give you an accurate idea of the colouring happening, but thought I would post now to see if you all had any thoughts.
heres some photos of the blooms. enjoy

[Evangeline Bourne]

I just went and had another look at it and noticed it was very loose in its pot, which it wasnt last week. so I gave it a gentle lift and it came out. MORE THAN HALF ITS ROOTS ARE GONE! and I found a small... creature in there... it looks like a miniature centipede? HELP so upset.