Could be not enough light. Plants grow up to reach the light. If they are getting enough par, they can grow bushier to get the light on more leaves.
20g platy, , 2 x 10g shrimp, 3 x 20g shrimp, 7.5g shrimp and 1 great dane/mastiff puppy.
Sump Pimp #2
My Tanks and my shrimps