You can afford to go a little heavy in the beginning I think. You have to remember though the problem with using food is you have to wait for it to break down for it to become testable phosphate, that being said the animals themselves will benefit from eating a food high in phosphorus as this should help them not be starved for it (in theory). So don't go hog wild, but you can probably feed more than you ordinarily would. I doubt I would do 3x a day, but feeding a nice broadcast feeding at night when everyone has their feeding tentacles out every day for a week isn't going to hurt your system.
Drawman is right, there is always the potential that the shock of the NO3 and all the waterchanges have cause the SPS to be unhappy. You won't know until you can test and build up enough data to be able to see trends in your nutrient levels. In the meantime feed your corals and fish and get them fat and happy!