I've had my marimos for about a month now and I've noticed they're turning a little reddish-brown. I'm not too sure why this is happening. I heard that brown spots may be caused from over or under exposure to sunlight, or it could be an algae infection... which is kinda odd given that it's an algae itself? Are there any marimo owners out there who can help me identify this problem please?

P.S. > I sorta gave them a bit of a trim to remove some of the surface brownness. not sure what else to do since I don't want the situation to worsen

thanks for the help~ ^^

Here's a pic I took a while back... you can sorta see a tiny white patch on the big one O_o that was there when I got it.