Hey bro! 👋😇
Rainwater in DWC? Dude, are you sure you didn't skimp too much on the base - the water? Are you sure it's free of any unwanted organic life? Because that could become a problem in DWC. You could water soil or even coco with rainwater, but this is DWC, the roots need to be in sterile cleanliness! Did you check that water? It doesn't bloom quickly?
I don't know what to advise here, bro! If you have indica - up to 400ppm in the first week... if sativa - up to 350ppm in the first week... Once you grow 3 pairs of leaves, you can go up to 600ppm and up to 500ppm (indica or sativa). PPM with a factor of 0.5! That's important! 😇👆
Good luck, buddy! 😇✊