Brown rusty spots on my critical 47?

I'm thinking its a Ph issue due to i didnt have any Ph Down but just got some yesterday so i transplanted into 1 gal pots from my starter pots cause i thought maybe a root issue also.If anyone can help me out and think its something else please have at it.

600 watt cooltube
watering every three days ( high ph around 7 or so due to hard water)fixed now phing at 5.8
40 to 50% RH
temps 78 degrees
soil my own mixture perlite ,vermitulite, peat ,worm castings and ro potting soil

I am having same problem with my 2 ladies. I water using tap water with fox farms nutes. PH'D after adding nutes to about 6.2. Its happening on both of my plants, but more so on the plant pictured. I am doing indoor soil grow using cfls. Mine is happening around the outer edges of lower fan leaves. New growth looks fine.

i know its a ph issue just trying to confirm ? urs looks more like a mild nute burn

I hope that's all it is, I was worried it was mites. Didn't see any when looking through magnifying glass. This is my first grow so I am doing alot of reading but this was a new one to me.

Usually if you had a mite prob you would see some webs plus they would b everywhere!!

Thanks for the info, I didn't know there would be webs. Just thought I would see little spider looking bugs.

Have you used a magnifier on the underside of the leaves? That's where the mites "might" be hanging around at. As far as webs, they are not always around when there are mites. Everything you listed seemed in the range, but glad you stopped using 7 ph water.