Not fade. Nitrogen moving into buds starts at the bottom and works up, top stays green. Yours is yellow top to bottom, evenly.
Different problem. Tip burn at the same time says it isn't simply hungry either.
If she's photo, 36 days is mid not late.
GNick55 asked the right questions and they're still sitting there. Answer those first.
One more, and it's the one I'd want: what size is that pot? Looks small for a plant that big.
If the newest growth at the very top is properly green and only the older stuff is yellow, ignore me, that's fade after all.