I would recommend not using them pH strips. We are not trying to figure out a "general range". You need to be precise. A pH meter that will get the job done can be picked up for under 30$.
I don't see the water temp of your solution?
Can ya add that.
I am thinking, 1.) your water temps are not in range, or 2.) you have a lock out because your pH is not right. or 3.) Your not doing things right, see footnote
If you can add more I will subscribe to this post and check back later to add on, or if you wish message me and I will respond threw the site private message feature.
*Is there any FAQ Tutorial or something you have been following? Also is this your first time growing? Stepping into aeroponics for a first time is doo-able, but you are going to see many problems and possibly, if you make it, a very great learning experience.