No, you don't need to vote again. Getting more ark into your account increases the voting weight which can in turn give you more ark per day from voting...
I have a question (probably a noob one) about voting for delegates. For example, if I vote for a delegate with 50 of my ARK (costs 1 ARK) and then I add more ARK to my wallet from an exchange, do I need to vote again (1 more ARK), or does the 50 more ARK I add automatically be applied to the delegate I voted for? Thanks.