help!!! pics attached

the basics 3 plant bubler using r/o water no nutes plants range in age with the oldest being 17 days from seed I have had some ph problems but I stay on top of it and bring it down it has been fine the last 24 hours but all 3 plants are droopy and have these spots they weresmall rust colored yesterday but look more brown today and seem to have spread not to the new growth but to the lower leaves the roots look good no slime what is it guys