Yes mate.
So, this isn't sooo bad.
As your buds haven't fully grown, it's not a right off.
So, what you need to do avoid this.
RH is a factor. But you can grow in 60-70% RH I do. The key is ventilation. You must have an exhaust set up to suck air from your tent. (It's called a negative seal)
So, to treat this. U can do a few things. Speed up your air exchange and MAKE sure your plant has no stale air in its environment. So oscillating fan will be ideal. You just want your swaying a little.
Your plant is young. Have a quick look with a loop. Check your young buds. If you see what looks like spiders webs. Then your plant those buds have had it. They'll need to be removed. 15-30x loop or a good Marco camera on a new phone
So, the parts that does have WPM, mix up a H202 solution. 1-5-10 H202 (3-6% can be got in any chemist/pharmacy/health store), make a wash, use a cloth and wipe your leaves down. You can also lighly spray the whole plant. (Cover your buds with hands and spray close) then you need to wipe down. Do this outside your tent
Then, spray your whole tent down, (a stronger solution you can use). Wipe down. KEEP UP VENTILATION. It's actually not from high RH, yes, it's a factor of course. But as I said. My crops, espically my last one. I had 30-35 plants going and was rotating them in & out of my 1m2 & 70cm2 (as a dark tent for the day). And my RH has been from 70-63 my ENTIRE crop. And I've just harvest the best weed of my entire 6 crops. Not 1 bit of bud rot. Ventilation is your friend. Also, move plants around. Those who are at the back. That don't get a lot of airflow, moving them about will lower this again.
GL and feel free 2 mes me, regarding any of this..
But please check your buds for white strands.