got rust on my babies! on older fan leaves, towards the uper half of plant. Would like to find out how to get rid of it. I grow DWC and try tokeep my ph between 6.5 and 6.8. I'm coming up to a change of water, as the last few days i've been topping up with 5 ltrs of PH'd water every day they drink heaps!. I change weekly.i was thinking it could either be mould or a cal-mag def but not sure. only 2 of 5 have it and other than that everything looks sweet. Any help or advise would be much appreciated.