There's a lot to unpack in that question.. Organic growers don't feed their plants.. They feed their soil.. That's the first issue.. Second issue is the ph of 5 you mention. Like how? Either you're purposely adjusting the water to a ph of 5, or you're using sewer water. No drinkable water has a ph of 5. So if you purposely try to break the soils buffer it will eventually happen. It will take a couple of months, but if you try that hard to break something, you'll eventually do it..
But in a realistic situation using drinkable water whether it's RO, tap, distilled, rain water, well water etc.. When growing "organic", none of those water sources need to be ph'd. And it will never cause a lock out or effect the soils ph. I grow in no till organic pots and don't ph anything. That's why you may have heard people say that you don't need to ph when growing organic. Ph'ing of any liquid has to with the nutrients in that liquid.. Anything with an npk value that You mix with water, should be ph'd.. You don't feed liquid nutes when growing in a true organic style. It's mostly water only like in nature. And that water doesn't need ph'ng..