first mead out of the keg very acidic?

[Jako]

Pulled the first glass off and dumped it, my second and 3rd glass very sharp and acidic. but i did noticed on the last one it was not as bad.

well i just pulled a 4th one (not all at once) and its sweeter little more flavor and body. someone explain this madness please. i wouldn't say its night and day difference but 5-10 points max FG points in flavor if i had to guess.