HELP... Yellow Leaf Edges! Potassium deficiency?

thanks stinky.... cleaning my res and going to try to rebalance the pH... will let you know how it goes

So, i flushed each plant individually with approximately 1L of pH balanced water earlier today. Since i was out the rest of the day, i set my res timer for my ebb & flow table to run once in the afternoon (figured i should kept the babies well watered, but did not add feeding solution).

Upon returning I noticed that my once drooping leaves were now angled upwards towards the lights (definitely a good sign of returning vigour, right?) and so rebalanced my res pH to 6, adding my feeding solution at 75% (didn't want to shock them bring it back full strength right away). I will closely monitor their progress over the next few days and flush again as necessary.

This is probably a noob question, but how often should i flush my plants? Do i do this on a regular basis (ie. with every change of my res water = once a week) or should I only be concerned with doing it when noticing major plant problems and before harvesting my bud?

In an added note... my run-off is running a pH of 7.5, which seems way too alkaline to me. I can't say i've measured it in the past so i have nothing to compare too. I know that rockwool has a tendency to make water more basic as opposed to acidic, and considering my run-off drains back to my res i know i may very likely run into the same problems i've just had.

Now to the question: Should i risk running my res water a little higher on the acidic side (5.5 or more acidic) in the hopes that my run-off will balance somewhere in the range i want it to be (5.8-6 pH) ?

OR

Am i just detecting the remnants of the Neutral pH solution i flushed with earlier today?

I've been getting conflicting info from different threads i've read, so a little reassurance is greatly appreciated as i get ready to prep for cloning at the end of this week. Thanks again for all your help!

If your runoff is still high, you can hand-water the slab with pH 5.5 until you get it down around 6, and then preferably change your res. IF you don't want to do this, just drop your res pH to ~5.6-5.8 and you may notice it rising gradually back up. Continue to adjust it to slightly lower than your target until the drift stops.

You don't need to flush unless there is a problem. But change the res every 1-2 weeks to prevent nutrient imbalances.

Next time, pre-treat your RW by soaking it down to pH 6 and then shaking out excess water before introducing plants. And when you stack some paper, grab yourself an EC meter. These things are REALLY useful to hydro growers. You may not NEED one sicne you are good about res changes, but when the time comes that you want to dial-in a strain perfectly, an EC meter and a log book are your 2 best friends!