I have 3 plants in autopots - I did a water change the other day – any suggestions
No expert and certainly no auto pot experience. Search above for info on PH. I do believe that 6.77 is high though 
@OGIncognito is an autopot guy. It looks like a touch too much nitrogen to me.
Appreciate the tag @MidwestGuy . I would say nitrogen rich for that stage and the PH should be 5.8 in veg and 5.8-6.2 in flower. PPMs around 600-700 at this veg stage. You’re probably going to have PH spikes with those res temps 
Thanks for all the info- Midwest guy thanks for tagging OG - I just went down added a gallon of spring water - plus 2 tbs of PH down - stirred it real good - I do have a water pump/air stones in bottom - I’ll check it all again later today when it gets a chance to settle…
Speaking of experts- @OGIncognito and @MidwestGuy got ya covered. Good luck
Sounds good Grow Bro, I would check the res PH periodically. Wave makers may be an option to the air stones as they move the water around
You can throw some frozen water bottles in the reservoir to help keep the temperature down a little. As the good advice already given, lower ph and tad too much nitro.
Just make sure the bottles have no contamination before going into the reservoir. 