Yellowing leaves - nutrient deficiency?

Hi folks

I’m currently around 2 weeks into flower and having some issues with fan leaves turning yellow.

I’m growing auto lemon haze and auto zkittlez under an LED in 5l fabric pots with BioBizz light-mix soil. The plants are watered every two days or so depending on the moistness of the soil and I’m feeding BioBizz nutes (bloom, grow, alg-a-mic and topmax) following the BioBizz feeding chart. I’m also using Vitalink calmag.

I initially thought it could be a calcium or magnesium deficiency so added some calmag to my feeds, and also thought it could be manganese deficiency. I’ve been having some trouble regulating the PH of my soil (my tap water sits at 7 un-PH’d and the PH of my soil was sitting at just above 7) so I started adding some BioBizz PH down to my water to make it more acidic.

The yellowing has worsened over the past few days and I’m kind of at a loss as to what’s going on. One fan leaf on my lemon haze has turned completely yellow with brown patches, and other leaves on this plant and my zkittlez are starting to show yellowing starting from the inner part of the leaf and creeping outwards.

I’ve included some pictures below. Any advice is greatly appreciated!

 

Thanks for the responses guys.

I flushed the super lemon haze to bring the soil PH closer to 6, fed some nutes and did a foliar feed of epsom salts but the issue just seems to be getting worse?

I’m not sure if I’m underfeeding or something but the whole plant seems to be turning yellow.

Help!