Are amino acid tablets healthy for you?

No. Well balanced diet is what you want and need. Amino acids may be deleterious to your health especially with constant use or lage amounts. The literature is not well defined on this but there were cases that suffered from serious side effects relating to Amino Acid supplements.
No. You would need Amino Acids if you are found to be low or lacking in one Amino Acid class, it is best to address your overall protein needs in relation to your metabolic status, consult a nutition specialist.