I recently bought some loose Assam black tea from an Indian grocery store and have been making it almost daily. I had to figure out the right timing at first, but I got to the point where I was making tea I was happy with. Then, maybe a week or a week and a half ago, my tea started coming out bitter even though I haven't changed anything. The steeping time is the same. I've tried using the water before it gets so hot, but I either end up with bitter tea or weaker tea, and compensating for weaker tea by increasing brewing time made it bitter. I'm so frustrated because I don't know what else to try. Could it be a problem with how I store it? It's in an open foil pouch inside a sealed Ziplock bag inside the box. Is a tin better? Does temperature matter for storage? Did I buy the wrong tea or something?