Im using a mixture of coc fibre white and and black pear worm humus, perlite pre fertilised 14-16-18
Ooooook. Um, let's pick this apart from the top. You plant has some clawing due to high availability of N. Nitrogen is most available in soil from pH 6 - 7.3 so we know your in that range.
Next would be phosphorus which in high amounts
reduces the plant's ability to take up required micronutrients, particularly iron and zinc, even when soil tests show there are adequate amounts of those nutrients in the soil.
Potassium is high but heavily used in all phases of growth. But it's worth noting that Soil
with a potassium level that is too high can prevent plants from uptaking other nutrients. For example, plants may be deprived of zinc and iron when potassium levels are unbalanced.
PH is always a factor not only the ingoing pH of the water but also any minerals it may contain. High calcium or bicarbonate will fix your soil with a high pH over time. Regardless of what the substrates pH is.
If your confident about the quality and content of your water and the pH is within range, I'd be inclined to believe you have too much phosphorus in the soil. Over time the phosphorus causes acidification if not taken up similar to sister elements. Also, overwatering and cold temperatures affect the availability and uptake of phosphorus.
You can expect to see micronutrients becoming deficient if not corrected. Flushing isn't usually recommended but I may advise it for this instance. All 3 of your macros are easily leeched away in pots.
You may see improvement after the flush. I don't know for sure, I've never used anything like that.
The nutrient charged perlite is your cause. If you can transplant I may go that route depending on how extensive your roots may be.