Think its a magnesium problem HELP!!!

Ok, im 4 weeks into flowering, my ph is around 6.0. Its tap water. Ive heard that the water here is a little hard. The leaves start to have yellow spots, then later turn into brown crispy blotches. They alos curl upwards.

Is this a magnesium problem?

yea man, looks like it. try to use some epson salt mixed into your water. good luck. aloha