i disagree with the folks here, i think it's a magnesium deficiency because of the yellowing between the veins affecting the oldest growth first. It's very slight until now and very easy to fix. based on how much you already put in i would say it could even be lock out. However i see you're at pH 5.9, try going up to 6.2/6.5 because magnesium and calcium get chelated at slightly high pHs which is maybe where the problem is coming from. Hope this helps ! 🚀