What is this stuff in my tea?

What is this elastic brown stuff in my tea?

This might not be the right subreddit to post this on, but I am so confused. I made tea the way I always do, an inch of milk at the bottom, and pour in the tea from my thermos containing 1 teabag, two packets of sugar, and hot water from a water dispenser. I drink about 6 cups of these a night working night shift, this has NEVER happened. I poured the milk (just purchased and just opened, BB Jan 31) and then poured the tea. It caused this stuff to float to the top, the milk did not mix in and almost instantly caused this thing to appear.

I know it’s not curdled, I tried mixing the same amount of milk with the same amount of water from the dispenser and it mixed perfectly fine. The only two factors I did not test are the tea itself and the sugar.

Incase it matters, the texture is very rubber like. It has no odour, and I did NOT taste it.

Any ideas?

If this is the wrong subreddit to post please let me know where would be more appropriate.