Do you know the TDS/PPMs of your tap water? You can grow with tap if the TDS isn't too bad. The higher it is, the more it can cause symptoms like yours. (Mine is 800 and I can't grow with it. I mix tap and RO to get to 150.). That's something you can find out from your water provider. They should know the average (even the compoistion of those PPMs, how much is bad stuff like sodium.).
You can grow with that fertilizer (not knowing the name, but an NPK ratio of 1-1-1 will grow. I'm doing
one right now.). And, you should be able to use it without ph'ing. (I don't ph.).
How much do you feed? It could be you're overfeeding, developed salt buildup, and that's acidified your soil (I see others have suggested ph problem. That's the only reason I mention that possibility. Watering with 20-30% runoff can rule that out.). It's common for salt-buildup to rear it's ugly head in early to mid flower.