Canopy leaves yellowing ph issue maybe?

Here are my auto zkittles 8 and a half weeks from sprout, I've noticed the front two are yellowing significantly up in the canopy and a few of the lower fan leaves as well .havnt had any issues all grow and these 2 have been the healthiest looking out of the five, I am puzzled because my run off ph is in range I'm growing in canna terra professional so my ph range is 5.8 to 6.2 I may have drifted up a little bit as one of the runoff tested at 6.4 have since got the ph back under 6.2 last watering. I've been using g canna flores, calmag and bat guano total ec 1.6 to 1.7. They have been nice and green all grow long I reckon they have 6 weeks left till harvest so could this be the start of senesence? I don't think so. I'm thinking lack of nitrogen or still a ph issue, any advise from more experienced growers feel free to lend me your thoughts

Here are some night shots, you can see the colour better it's just the canopy that's really losing colour everything underneath is nice and healthy looking as you can see in the last shot. I'm using a ks 3000 and it's 30" above canopy ppfd is about 630 surely its not light stress? Gotta be something else, I only water when the pots are as light as feathers I'm puzzled. Growing is always a roller-coaster and I hate asking for help but I think I need some expert opinions thanks in advance

canna flores, calmag and bat guano? It looks like a nutrient lock out, you used a wrong combination of fertilizers, too much phosphorus can lead to nutrient deficiencies like iron.

Skunkee101 said:

canna flores, calmag and bat guano? It looks like a nutrient lock out, you used a wrong combination of fertilizers, too much phosphorus can lead to nutrient deficiencies like iron.

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Oh OK to much phosphorus you think thanks for the input