Looks like you need to recalibrate your ph tests or its nutrients or poor watering practices. From what little i know. Thats the only things that can this. Over or under watering can cause this. Nitrogen deficiency can, as well as too much nitrogen. You are 100% sure its not ph. I would look closely at what you are feeding and if they're being watered correctly. how long between watering? I wait until its fairly dry up to the first joint on my middle finger if i stick it in the soil.