I'm not sure what you growing conditions are at the moment. Is it cool? dry? Are they in very bright sunlight? Keep them well watered depending on your daytime temps. You want to make sure that roots have turned overall dark green when you have finished watering. Two applications of water to the point of runoff spacing it several minutes apart should work and you will notice a color change from white to totally dark apple green. Saturated roots are absolutely necessary to provide moisture the plants need to withstand heat and dry air. Vandas are big feeders I would try to fertilize at least once a week, but weakly. It is spring here in the Florida. There are new roots busting out and many species are in bloom. But vandas do just hang there. That is their nature till they bloom.