Thanks, Weedhound. Yeah I have the chart for the various nutrients and their proper ph ranges etc. and have been keeping it at 5.8 as perfectly as I can. This rapid dropping thing is a new one.

It's at 5.7 now.

When I rearrange my room this evening, I'll raise up my grow tub a few inches so the system will hold overall a bit more water. Should make it more stable in general, and keep water temps cooler too.

Despite it all, the plants are doing well, crowding each other, showing pre-flowers and starting to give me a nice smell