I realize the lights are on the high side, but nothing is showing evidence of leaf burning. The large phrag in the back is a Peruflora's Angel that has slight yellowing of its leaf tip, but other than that, no damage to anything. Growth is in fact quite strong for the group, just this splitting issue that arose recently. I can't say for sure that there was no prior evidence of splitting before enclosing them, but it has definitely gotten worse or accelerated. Some new plants/seedlings have only just started splitting.

Maybe it is light intensity related, but I have to think there's more to it than that. I'll move the fixture further away. I'm also going to get a different fan to reduce the airflow a bit. I have a CO2 bag that I'm trying out on the top shelf. The enclosure isn't fully sealed off, so it gets some air exchange at the bottom of the shelf. I also open it every morning to water anything that is close to dry.

Here's some pics I took today of the splitting:

https://dl.dropboxusercontent.com/u/...222_171103.jpg
https://dl.dropboxusercontent.com/u/...222_171123.jpg
https://dl.dropboxusercontent.com/u/...222_171207.jpg
https://dl.dropboxusercontent.com/u/...222_171223.jpg

I don't really grow these, but just seems like the splitting should be caused by either being too dry or too hot. I do use the t5s and it get very hot when you are that close to them.