I also had a tan batch recently, funny you say it seemed weaker, I did think that it possibly was weaker also but I thought it could be just dissociative permatolerance.
I did however find it to be a bit easier physically somehow than a batch I had several years ago which came as white square crystals like table salt... I guess it's possible also that differences in purity could account for those differences, though... I guess it would make more sense for white crystal to be more pure than a powdered, colourised variant.
Pretty hard to compare overall over longish timespans. I guess there could be other relevant differences too in my substance use and general lifestyle habits between my experimentations with each batch.