Rising to 7.0 is not healthy, and for some reason this has happened to a lot of us that have ordered the SH system. Took me weeks to figure it out, i'm pretty much an expert on it now so i'll give ya run down, lol.
How old are the plants, are there roots yet? If so, what do they smell like... are they brownish in color?
Is there anything dead and/or decaying in the water? Be it the roots, bugs, anything else dead. If so, remove it.
What are your water/air temps? Do you use any additives and what kind of nutes?
What kind of water do you use, if it's tap what is the ppm of your water when it comes out of the tap and the pH?
If your using tap water, and you don't have a ppm/pH meter it could very well be your tap water causing problems. Buy distilled water from WalMart (76c a gallon) and see if that makes a difference.
Is your water greenish in color? Do you have any slimy material on the bottom or sides of the resevoir, if it's green then it is algae and that is your problem.
Did you SOAK your rockwool cubes and hydroton rocks in pH correct water before adding to the tank? If you did not, then the pH is unstable because of them most likely, you could take them out and soak them in pH correct water if you are not far into your grow... or just wait it out and eventually they will stabilize. Use distilled water and it won't be as bad.
Check your feeder tubes, are they the same color they were at when you got them? Are they green or brown, if so they are clogged and the tubes need to be cleaned. Put the pump in like 5 gallons of water, attach the feeder tubes add a light amount of bleach and run the pump for a couple hours your tubes should be clean. After that, run the pump w/ the tubes attached in clean water for a while and make sure all the bleach is washed out.
If none of this is the issue, do a full drain and replenish. Take your res, SCRUB it well get it sparkly clean, use some H2O2 or bleach, if you use bleach make sure you rinse it out real well before use again.
Something is amiss in your tank if your pH is rising so quickly. Try/respond to all that I said, and I we can eliminate the problem here and get your pH under control. Best a luck to ya! You will get it straight soon enough.
Also man, check out this thread.
https://www.rollitup.org/dwc-bubbleponics/7897-stealth-hydro-bubbleponics-systems-1019.html
You will find lots of help here, and if you read over the past 150 or so pages you will find every answer to your pH issues you have ever dreamed of, a bunch of us went thru it, lol.