plants growing up not out

[thelub]

I have some clippings that are starting to come around, but they seem to be growing up a lot, but not out much. All new growth is all at the top. Is this a side effect of a low tech tank?

Setup is a 55gal
sphagnum moss with a sand cap
(2) T12 bulbs. One 6500k and one 5000k
no firts, no CO2

plants:
Ludwiga SP Red (up, not out)
Cabomba Caroliniana (up, no out)

Blyxa Japonica - (not doing very well. growing, but VERY slowly)

There are a couple others that are growing, but they seem to be struggling.

Water hovers around 76 degrees steady and water parameters are perfect (ph 6.8, ammonia 0, nitrate 0, nitrite just over 0)