Doubts on Definition of Indistinguishable Encryption in the Textbook
Depends on how different your algorithms are. If you can compute $A_i$ from $i$ in polynomial time, then $A'$ with $A'(n) = A_n(n)$ is a polynomial time adversary too and violates the assumption (as it has non-negligible success probability). This would make your series of $A_i$ uniform and is one usual class of adversaries to consider.  

If you'd like your crypto system to be secure against any such series of polynomial bounded adversaries you have to consider non-uniform adversaries (at least non-uniform in polynomial time), by e.g. defining a single adversary as a series of (randomized) circuits with polynomial size.