Ablative Bottom Paint

[abiscow]

So, not a first time boat owner but new to a boat that has come from the salt. Sort of a warmish day compared to the twenties we've had. Starting to clean swim planforms and the green algae off the waterline. As I'm brushing the algae stains,]I find the black bottom paint is coming off when I get the brush near it. So, internet search and voila. Ablative paint. So that's ok then. My question is can I just touch it up w the same type of bottom paint or do I need to consider doing the whole thing over. The rest of it looks ok underneath.