Brown leaf tips in phrags are either not enough water, or more likely, salt build up, which your rainwater soaks will definitely help with! I imagine a good "leach" once a month or so will help (water well, wait an hour, water well again). Theoretically, proper S/H shouldn't require this, so long as your fertigation water is the right concentration for your plants.
I wish I had somewhere outdoors - I live on the second story and "garden" in an enclosed balcony!
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