The volume/amount is fine if it's done every day. There's a difference between runoff and spillage. If water is coming out of the sides of the fabric pot, or just leaking down the sides of a plastic pot, that's spillage, not runoff. But if you're using bottled nutes at half strength, then whether or not you get run of shouldn't matter. I strongly doubt that salt build up is an issue at half strength and using the FWWF schedule. At this point you just want to get them to the finish line. But I'd up the feed from half to 3/4th or full and see how they respond for about a week.