Limnophila hippuroides stem breakage

[JJP2]

My Limnophila hippuroides grows to about 6 inches at which time the top couple leaves begin to turn purple and the top 2 inches breaks off. The stem is also fairly thin about an 1/16th - 1/8th inch. They have numerous leaves which are currently staying green with only a few at the top turning a purple.

Any thoughts on why they keep breaking off?

Thanks,

 

[VaughnH]

As usual, it helps if you tell us the details, like tank size, lighting, fertilizing, CO2 method, etc.