The dendrobium blasting it's buds; I would check the roots. Too often, the care given at a greenhouse, and the care given at the average store are worlds different. Once at the store, usually they are overwatered. Then when you take them home, once again they are in a new environment. The changes can cause the blasting, or bad roots can cause it. When you first bring home plants, often they need to be repotted. Your bulbo looks like the potting material has gotten very old and dark looking. This would be a good one to repot soon. And the third plant is looking very crowded, i'd repot as soon as it's done blooming, sooner if leaves begin yellowing or if these buds begin blasting too.
There are care sheets and repotting articles that should help with each of your plants. A few quick searches of the articles should give you alot of information on your plants.