I wouldn't personally recommend putting amanos in such a small tank, nor would I recommend putting shrimp in a tank as young as that is.
Was the tank cycled? What are nitrites at?
It may be a good idea to raise the light up and/or put a "siesta" in the middle of the light being on... i.e. 4 hours on, 2-4 hours off, 4 hours on. That is, in addition to doing the plant dip to get rid of the algae.