Vaeira Exile and Redemption (096) The first three plagues punished the Egyptian gods, only from the fourth plague and on were the Egyptians themselves being punished. Therefore only from the fourth plague on was the difference between the Jews and the Egyptians very noticeable.

Vaeira Exile and Redemption (097) Continued. The Midrash sees all the מכות beginning with the very first as a series of steps to exhaust Egypt, accordingly ערוב wasn’t about killing Egypt but to confuse them, thus the name: ערוב.