Hey mate.
If i had a root pathogen, id remove the plant temporarily, clean and sanitize EVEREYTHING. First. Lines, pumps, res, drippers tent everything. When ive had it in the past, id just buy new lines and feeders aswell to be safe.
ill just list what id do concrning each points you raised 1-6.
1. Temperature reservoir - keep it between 18-20 degrees c
2. Light leaks - IMHO by the sounds of the see through guage you have on the sides of your res/buckets, is our problem.
3. Hydroguard - i dont think it could hurt but i havnt used it before
4. Slf 100 - dont think it would hurt either.
5. Watter swapping - Id be swapping it 1-2 times a day, fresh. You have rot. You cant let it fester. Also reduce the nutes a little and lower the res in the dwc. To give the roots some oxygen to help the plants try and fight it off.
6. Id still be weary about not enough oxygen though. They cant really have too much unless its like a washing machine in there.
If it kept comimg back, id be sus on my water.
Hope this helps dude.
Tim
I transplanted plants in soil , to coir ( still got root rot in coco coir ) and then I went to 90% perlite 10% coco coir . To get rid of my root rot , I discovered a new technique to water , feed , and air out roots , and apply root rot medicine ; that is probably how I ended up with powdery milder and black wet mildew ( I am guessing the root rot pathogens can move up the plant into the leaves and look like white or black or brown mildew ) . At any rate I found out that I could use calcium nitrate and two amino acids L-Glycine and Glutamic Acid , for white powdery mildew , so I figured it would probably cure my root root , the theory being that sometimes they might be inter-connected . So first of all , the perlite enabled treating a plant , watering it , and feed it things like nutrients or other products , in rapid order because the perlite drains so fast that I can go through all of the cycles in about an hour , So first I treat the plant with the calcium Nitrate and the Amino acids in a water solution and pour through the perlite . Place a container around your pot so that no drainage occurs and let the plant perlite root zone sit in the solution for 15 minutes . Next I drain the perlite growth medium of the plant and let it get air on the roots for 15 minutes , Next I do the same thing , but with water . Let the plant drink water for 15 minutes . Next drain for 15 minutes to air out the roots allowing the plant to uptake oxygen and for the roots to absorb oxygen . Next I submerge my pot of perlite plant in my nutrient solution for 15 minutes submerging the roots . Next drain the nutrient solution and air the roots for 15 minutes . Next I look at the color of the leaves and see if they are faded green or sea green ( my nutrient solution includes kelp or seaweed and seems to make my leaves a somewhat dark green ) , If the leaves looks flushed of nutrients I repeat the feeding of nutrient 15 minute root submergal again and then drain for 15 minutes to air out the roots . This now usually means my plants have enough nutrients to last a few hours or move . I am assuming my root rot is healing and I am seeing much less powdery white mildew and less brown rot on some lower leaves . As it turns out , going through this many step sequence method , I end up with a rapid growth result for my plants because I now believe you can dramitically speed up robust plant growth by shorten the water , feeding , drying of roots to get air , flushing , this entire routine that you get with soil can be speeded up in perlite to one hour , that which takes a week in soil . And since I am stressing the plant some with my method , I treat my plants once a day with my calcium nitrate amino acid solution once a day . The draw back is I am wasting a lot of water and dumping nutrient water waste into the sewage system . Now all I got to do is automate the entire process and find a way to purify my water waste and desalinate the salts in fertilyzers , I end up with the fastest most robust healthy looking plants with fast branching and fast leaf growth . We will see how my buds look when I get there . I am writing a computer flow chart and figure out what equipment I would need to automate the process I am using , but the basic concept allows for periodic root drying time in almost pure perlite or entirely perlite , in 15 minute intervals for each step . Based on that , you would never have gotten root rot with this method I fell upon , but I used it initially to heal the root rot . In other words , i gave up on soil or coco medium , ( I use coco coir medium to clone but perlite to grow in ) .
It might take me a year or two to figure out how to automate the process , because doing this method manually is almost a full time job . After I go through the cycle to my satisfaction , I take a rest by placing each plant in water so that the bottom of all the perlite of the plant pots are submerged in a half inch or one inch of water , but the roots not submerged in water and the wicking action of the perlites keep the roots moist . This is to prevent the leaves from getting too dry ; where the curl up and look half dead.
I know that my system will take about a year to automate , but one can find other ways to use perlite as a growing medium. Either way , growing in perlite makes it almost impossible to get root rot . You can suffocate a plant if left in water submerged for too long , but at least it would not die of root rot . LOL
Halman9000