Janet, this is a Keiki but there is nothing to worry about. The media on which orchids are germinated or rooted frequently contain artificial plant hormones like NAA or giberellic acid analogues. Hormones like NAA have a tendency to cause indefinite growth that is there is no termination of the growing pseudobulb which would have occured naturally in the absence of the artificial hormone.
Once the plant grows and matures further, the NAA it has accumulated in its tissues will slowly be degraded and you will not see this effect. One important thing, you might have to check all your fertilizers etc that you are spraying on these seedlings, if they have plant growth stimulators etc, it can also cause this effect. Just reduce the dose if you are not sure. Once the plant has matured, it has its own set of regulatory networks that will inhibit such kind of behaviour.
Another aspect is to look out for the pedigree of your plant, if it has a lot of epidendrum influence then you can expect to see Keikis.