Could be the calmag? Whats your water like?The only feeding I have done is a top dress of fox farms fruit and veg mix and raw cal mag in with the water.
I wouldn't be ph down the water,soil has buffers in it like lime to control ph.My tap water is 7.2 ish and i dont adjust it.That same lime is also your calmag so i dont think you really need to add any.I’m using tap water letting it sit for 24-48 hours then phed down to 6.2-6.5. The town I live in has 3 artesian wells that our water comes from. However I haven’t had it tested