There is no need to re-pot based on the size of the pot. I have seen 4-5 fans in that size pot. If the medium is decomposing then re-pot in the same pot. You will usually do this about every two years. You have plenty of room. I use a combination of medium bark, coarse Perlite and a little sand.
Paphs with mottled leaves like shade and I would keep that morning sun only til mid morning. Mine are mostly mottled leaved so they like it a little warmer. I keep them in the house during winter here. Outside they grow at the base of my Psychopsis in the shade. The Psychopsis gets more light at the top of the stalks.
Here is what I copied from Sunset Orchids on catasetums
Early spring:
Catasetinae begin their new growth in early spring. However, watering should wait until the new growth has well developed new roots. This means you should let the new roots grow to an approximate length of 3-5” before you begin watering. Let me emphasize this point. Wait to water until the new roots are well developed. The waiting to water is not easy, my natural instinct is to begin watering when I see new growth, but I have learned through trial and error that it is better to wait to water than start watering too soon. I also believe that Catasetinae roots deteriorate during dormancy and in the following year they are not as effective at taking up moisture and nutrients. This makes the new roots vital in the plants health. This reinforces the message about not watering too early.
Mid-Season:
Once the new roots are sufficiently developed, this is the period where the plants are rapidly developing their new pseudobulbs. There is a surprising amount of growth that occurs in these 3-4 months, often the plants will double their size. Due to this, the plants require constant moisture and regular fertilization. In most cases, irrigation will be need 2 or 3 times a week. A balanced fertilizer at full strength is suitable for this rapid growth. Light levels at or above those suggested for Cattleya will help insure strong good growth and flowering. This is the time when the fruits of your labor will begin to pay off as the flowering season is in underway.
Late Season:
Sometime after flowering, in the late autumn the plants will begin to enter the dormancy phase. Understanding the signals of the onset of dormancy and the factors triggering it are important is good plant culture. The plant first signals are the yellowing and browning off of the leaves, at this time stop fertilizing and reduce watering by ½ and when most leaves are yellow/brown and have dropped off cease watering altogether. The general rule to follow is: by the 15 th of November stop fertilization and reduce watering by ½. Most leaves should have yellowed or fallen off by the 1 st of January, however, if the plants still have leaves all irrigation should be stopped at this time.
The onset of dormancy is caused by several factors, the maturity of the pseudobulb, shorter day length, cooler day/night temperatures and a reduction of root zone moisture. In most of the country dormancy occurs naturally however when the plants are cultivated in warm growing areas such as in South Texas, Florida, Hawaii, or in the home or under lights sometimes dormancy needs to be encouraged. I have found that stopping watering in early January regardless of the number of green leaves will trigger the dormancy.
Note: Watering during dormancy should only be done it the plant shrivels severely. Usually a single irrigation is sufficient to restore the bulbs.
Here's a summary:
As the new growth develops wait to irrigate until the new roots are well developed and are 3 to 5” long. (don't be in a hurry to water, it is better to wait)
Irrigate and fertilize frequently while the plants are in active growth.
Stop fertilization and reduce irrigation by ½ around by mid November.
Cease watering by the 1 st of January.
Light levels: Catasetinae like light levels comparable to Cattleyas at about 2500-4000 foot candles (fc) However, the plants are widely adaptable and do well with light levels as low as 1500 fc and as high as 5000 fc. For optimal growth I suggest a Southern exposure or a location where a the plants will receive plenty of bright, filtered light
Potting mix: For mature plants I have been using a 3/1 of mix of fine ‘Kiwi Bark’ and medium Perlite. For seedlings up to a 3” pot size I like to use New Zealand sphagnum moss with the bottom 1/3 of the pot filled with Styrofoam peanuts. However, this genus is not too particular in what it is potted in and any well drained media will work well.
Containers: I prefer to grow in plastic pots, however clay pots, baskets, and cork slabs will all work. Catasetinae don't like to be over potted, select a pot size that will allow for 2-3 years of growth.
Fertilizer: When in active growth, regularly use one teaspoon of your favorite fertilizer per gallon of water.
Air movement: Catasetinae enjoy abundant air movement, if you are growing in a green house use air circulating fans. Also, hanging the plants allows for maximum air movement around them and often they do best hanging.
Repotting and Dividing: Is done as the new growth is just starting to develop and before the new roots start to show. (remember no watering until the roots are well established, 3-5” long). Unlike most orchid plants Catasetinae do well when divided in to 2 bulb pieces. Divisions are made by cutting with a sterile tool or by pulling the bulbs apart. I try to keep the size of my plants between 2 and 5 bulbs.
Insect pests: Catasetinae are generally pest free, however spider mites are attracted to the soft leaves of these plants. Spider mites are quite small, they live and feed on the undersides of the leaves. Take care in checking for them as the plants are developing the new leaves and control them with a recommended miteacide from your garden center. Although the leaves will drop off during dormancy this is not an excuse to not treat for them.
I bring mine in during the winter so they don't get any rain in the dormant cycle.
You may be resuming watering too soon. Mine have started to show new growth but I will not water until the roots get about 3" long
Hopes this helps
