I screwed up and told you to cut them down out of panic it was mold but I looked closer and clearly see you have mealy bugs/ fuzzy aphids. Get yourself a spray bottle and a bucket/large cup of water along with some neem oil or dish detergent, dawn is the best.
Mix 4 tablespoons of dawn/neem oil per gallon. You want it strong.
Spray from the top down. Top and underside of leaves.
When you get down to the infested area do this in this order
Spray the infested area until it's dripping wet.
Cut away all the dead material and seal it in a bag. Burn it if you can.
Take the bucket/large cup with the dawn/neem mixture and some kind of tool to scrape with. Scrap everything you can into the bucket/large cup filled with dawn/neem mixture.
Flush it when you're done.
Spray your plants before the light comes on from the top down, both tops and undersides of leaves with dish/neem mixture 30-60 minutes before the lights come on and just before or after the lights go off everyday for 10 days.