The growth buds are at the bases of the pbulbs. They are easy to spot. The optimum time to repot is when the pbulbs start to grow new roots. That varies with species and hybrid parentage. Some grow new roots about halfway through the growth phase while others grow them after flowering. It all depends. It looks like the pbulb that just finished flowering has some really good roots growing already which is what my ports of paradise does. It started growing roots about halfway through maturity. Peel those old dried pbulb sheaths off carefully and from the looks of the pbulb you will find two growth buds under there.
Actually you have three there. The upper one will probably not grow as the other two will take the nourishment but is anything happens to them the third will then take their place. The next older one should have one bud which should grow if moisture and light levels are right. Peel away some of the bark and take a peek. Good luck. I want to see these next season. They'll flower around June or July. When the new growth is about half mature try giving them less nitrogen and more phosphorus and potassium. Also up their calcium.