it's magic. use it any way you want to. LOL, not quite true, but the magic part is. This will not impact mineral content of buds. What it definitely does is provide a less-than-can-be-used dose to the plant over the time period you do it, which definitely slows down development. Do you flush outdoor plants? no, because you'd get laughed at, lol.
Flush is a tool for problems. Are you having a problem? is the plant showing extreme signs of toxicity or ph-issues related problems all over? if not, there is no reason to flush.