White hair on buds turning brown?!

It could be, but usually bud goes wilt and hair goes curly. White to brown changes naturally with maturity, but for week 3-4 even with autos it's too early. My personal mistake list for achieving your results : 1. Polination,, goes brown and shrink 2. Heat stress , goes brown 3. Wind stress or damage , goes brown and heavily shrinks 4. pH issues , goes brown, degrades slowly 5. Humidity with too high or low temps, goes brown, sometimes curly, diminish size of pistil quick, but looks like shit I found out it hard way, generally pistils colour is not an issue for end result, but any damage wich led to it - could be. Think what has changed and try to put them back to good regime. Otherwise your autos just running fast and it's part of maturity. Hard to tell with limited info. Don't forget it's part of flower and we want more flowers, because we smoke them, not stems leaves or roots. All the Best !

that's not light damage, Pistils just do that in flower they don't stay white forever. Light burn turns buds albino and crisps up the leafs. As for how close the light should be. You need to calculate its intensity in terms of PPFD or PAR. Once you know that then you can better gauge your lights height requirements. your light manufacture may have better information regarding general light configurations regarding its height, contact them. Good Luck and link your diary.