The acidic run-off is quite plausible, but are you sure your ph is accurate?
Perhaps a little extra limestone in the mix would help you through the rainy season...?
Rusty Trichome Reviewed by Rusty Trichome on . Suspected, now fact I have had problems in the rainy season with all of a sudden the garden looking like hell. I use RO water because of high Iron content, but even with the RO, I got times that were just terrible. I was starting to notice this always occurred during the rainy cold season. Well, we have had 21 days straight with measurable precipitation (Wierd season). For the last 6 months I have been monitoring my PH as the RO leaves me without Cal and Mag, which I add. The Cal/Mag always lowers the PH, Rating: 5