This just popped up on a few plants

So everything is going great per usual...in my 5x5 veg I was feeding a light Canna base- Vega nute, cannazyme, Rhizotonic, and 5 mls of cal mag/gal- in r/o water totaling my ppms at about 7- 800ppms ph'd @ 6.3, plants are in promix hp with a bit extra perlite...plants were looking healthy, lush and green...then I decided to check the run off...some of the plants had a runoff of 2000 ppms plus, other plants not really that high. So I decided to feed just plain water no nutes, I did half tap water- half r/o water with no cal mag till I got a decent amount of runoff which i got rid of.I did this for a few waterings when I noticed this slight yellowing spots on the a few fans...

I'm wondering if the plants being used to the r/o water with calmag did not like the sudden half tap water mixed with r/o and no calmag? I don't know...1st pic is spotted fan after a few no nute waterings..2nd and 3rd pic is last week, watering w/nutes in r/o plants all look healthy. Think I might ditch the half- tap, half r/o water, I like to do that just to save some water, r/o filter waste so much water...

The lime has probably stopped buffering your PH , so...its not acidic enough to have all availability nutrients for the plant. some will add more lime or PH TO 5.8 instead.

BenGman said:

The lime has probably stopped buffering your PH , so...its not acidic enough to have all availability nutrients for the plant. some will add more lime or PH TO 5.8 instead.

Click to expand...

Word ya I was thinking of going a little more acidic so around 5.8...do you think that the cause though? It seems to have come on rather quickly. I've done whole runs with half r/o,, half tap(thats sit for 24hrs+) with no problems, I have been using just r/o the for w while and I feel some strains that are getting nutes w/ r/o water tend to get not like it and can get finicky if I start using half tap water out of the blue.