help with one of my plants

I noticed this on 2 of the leaves today any suggestions would be great...only one plasnt is doing this everything like temps and ph seemed dialed in...

what water?
could be calmag

Using r\o water ph swings from 5.3 to 6 daily other plant looks fine identical setup

yep you should add some cal mag or mix with some tap water to EC 0.3.

thanx I will get some cal-mag and give it a shot tomorrow