Came back from anoter trip to find this, not bad but first time I have seen this. I think the cause is that my top off was pure R/O water without cal added. I added Cal to the top off along with a little addition hydro. In the past it was pure RO water added into a half mix of nutrients.
I should add, I started using Big Bud for the last two weeks, It could be a nutrient problem of to much P, backing off on the next feeding.
Any suggestions would be appreciated.