lol. teas have tannins which helps fight bacteria and fungi.
you need decaf green tea as caffeine is in no way good for fish.
many hobbyists use indian almond leaves which is a good source of tannic and humic acids for their aquariums. I was merely suggesting alternatives incase you dont have indian almond leaves on hand.
most importantly, right now you need good clean water. without a container, I can only suggest a 100% water change. my only guess is that something is out of whack with your water.
I'm going to sleep too. sorry if you didnt find any of this useful to you. need to get up in 3 hours. lol
goodluck to the fishie