African milk tree
A couple of the "arms" of the plant have become limp and I had to tie them up. What might have caused this? It's an indoor plant.
The Euphorbia trigona is know to have branches go limp from time to time.
Exact cause is unknown in your case, but check to make sure the plant is receiving good light but not direct sunlight.
Keep the soil mix damp, but not soggy.
In winter keep it slightly on the dry side.
You can prune your plant and even grow new plants from the cuttings.
This is a good way to keep the plant size in control.
Keep is mind that the sap of this plant is poisonous and care should be taken when handling your plant.
Use gloves and to not get the sap on your skin or near eyes and mouth.
If you suspect an insect or fungus; use Neem Oil.