Hi, hope it's not as serious as it sounds. Is there any visible damage to the plants? What are the orchids potted in? Can you see if it's in the potting media? I had something like this happen to me earlier in my orchid habit and the other members suggested that it may be a little creature that likes the bark the orchids grow in. If it is them, you may have to repot because they break down the bark faster. A pesticide safe for orchids may be another resort if you recently repotted. I use Actara or 85% Sevin solution, neem oil is a natural option too if they plants live out the intense sunlight. I'm sure you may find others mentioned here if you key in pesticide in the search at the top of the page. Hope these buggies make a hasty exit soon.