could this be due to the PH being too low?

Dunno, seems like you have asked 300000 PH questions before you should be an expert on taking PH levels why would you need to ask that?

They look hungry to me. Some npk problem i guess. For photoperiod i personally used biobizz as supplements and i used chicken manure and bat guano as main food for growing and flowering.

This is a calcium deficiency...........certainly NOT a phosphorous deficiency. Your pH is ok, you just need more calcium. Add a cal/mag supplement to your fertilizer line up or increase the dosage if already using one.

I'll say it's phosphorus your lacking, either through not enough in your feeds or through the ph of your growmedium being out of range.

This looks like probably a phosphorus deficiency to me. Were you able to check if any illness matches theses symptoms? If you are sure you are feeding your plants enough phosphorus I would aim to get a ph around 6.4 and this might already be the solution to the nutrient problem. So to answer your question: Yes it is probably a nutrient deficiency due to low pH. I just hope for you that, that's it.

Looks like CalMag Defizit

Hi bro, The observed leaf discoloration likely stems from a nutrient deficiency, potentially involving Magnesium, Manganese, or Potassium. Alternatively, environmental factors such as overwatering, underwatering, or temperature stress may be contributing to this issue. As the grower, you possess a thorough understanding of your plant's feeding schedule and environmental conditions. If a nutrient deficiency is suspected, I recommend adjusting the fertilizer regimen and considering the application of a foliar spray to expedite nutrient uptake. Ensure the plant receives adequate but not excessive water and that the growing medium provides excellent drainage. Maintaining a stable temperature within the optimal range for cannabis growth is also crucial. Best of luck buddy.