i need expert advice, been trying, rust spots,pics incl. rep++

i belive that this is due to low ph. and lockout. my soil tester(cheap probe type) reads my soil ph at 5.5. but if someone knows what this could be from, please help a brother out. the rust starts out on the veins of the leaf, then starts slowly crisping and totaly frying the leaf causing it to curl and die. Maybe nute burn? did just switch to beastie bloom. and if it is low ph, how can i raise the ph without flushing? i am using a scrog and have no drainige system. so flushing must be done with clearx or something. Using Fox Farm Ocean Forest and their entire line of liquid and soluable nutes. A thousand thank yous in advance. Super rep for any help

Strains affected are Platinum Kush, Cotton Candy Kush, and DP Blueberry