Fdk. After Dark Brown Leaf Tips
 

Attached is picture of leaf tip on Fdk. After Dark. Thee of the leaves are fine but the other three show this damage. I will flush the plant with distilled water as suggested. I checked for mites and found nothing. Thanks for help.

Could be a bit too much salt/fertilizer in the water, or too little water. They are basically the same thing, if the root environment is really dry the salt concentration is higher.

You probably also know that this plant is deciduous... So it is pretty normal to start seeing yellowing leaves at this time of year. Not usually starting at the tips though, for me the entire leaf yellows pretty much at the same time.

I agree with littlefrog.
Fertilizer crystals acumulte on the roots making it hard for them to bring humidity to the plant.
Also try to replant and change your media to a coarse bark, charcoal, sponge rock and clay hydroton.
Also check if theres a ball of moss under the roots...soak the pot well to soften the roots. That way you can flush it completely and then also see for yourself if theres dead roots and cut them off...cinammon powder with a bit of water to make a paste then dab the root wounds.
You can cut the dead leaf tips and dab with the cinammon paste.

Grow in intermediate to warm conditions with partially bright light. Water regularly during growing season and when plants drop leaves during dormancy reduce watering. During dormancy only water about twice a month to keep pseudobulbs from shriveling. Resume watering normally when new growths occur in spring. Plants can die easily from over watering. Plants are usually grown in bark, coco chips, cork with charcoal, lava rocks and clay hydroton. Female flowers will often be produced when high light and low moisture is present. While male flowers are produced in shadier situation of higher moisture.

well, my experience with Catasetinae is that there is nothing like "too much fertilizer" :) unless you really put A LOT of it! and I mean A LOT!! (have fertilize plants with up to 3 times the normal concentration I use for experimenting purpose, without any noticeable damage!)
But I have had similar browning of the tips when forgotten to water the plants for a long period...
By the way, even thought I never used 100% spahg in the past (now I am experimenting with it!) Most people have very good results with it and Catasetinae (repot every two years!). I am also experimenting with growing them in a mix of bark, perlite and sphag in clay pots sitting on 1 inch water all the time (great Results!!)

I assume the one inch water is a humidity tray?

grow them better in warn to hot conditions! (better than intermediate when in actiuve growth!) Water and fertilize intensively during growing season, as mentionned before, but keep dry during dormany (I normally water without fertilizer for 2 or 3 weeks before going dormant, to wahs out excess of fertilizer (this could affect the growth of new roots at the beginning of new growing season!).
af for the lips, no need to put cinnamon, just cut them off iffor stetic reasons. If the Pseudobulb already mature?

no, the pots are sitting in water! like S/H!

By the way, used to have most of my catasetinae in S/H when growing indoors. They love it! when moved to a greenhouse, I had problem with the method, that's why I am experimenting with different methods this latest growing season (best results: clay pots in water!)

When is the best time to transplant the Fdk? It is in sphag and is huge. I don't want to mess up the flower cycle. This is the only Cts. I have ever tried. Thanks again.

Before it starts to grow roots in the spring is my suggestion. Wait until it goes fully dormant, repot it, but don't water until the new growths are a couple inches tall or you see the old pseudobulbs start to shrivel.