Woke up this morning to find alot of my seedlings are developing brown spots . Did a runoff pH test on a few of them, and it came out at 7.4 using 6.5 pH water. Runoff was a yellowish color. Flushed them all with about 5 times their volume in water and could only get the runoff down to about 6.8. Runoff at the end was clear though. Hopeing they can bounce back. Any advice?