New plant owner. Just got 2 calatheas

I’ll take any help/tips I can get. I read online they like bright indirect light, moist soil, and warm temperatures. I’m using a grow light and they seem to like it. I usually keep my house around 67-68F. I noticed the green plant has a brown spot on 1 top leaf but the rest look great.
The other plant has little spots on a few leaves, when I got it last week it had a couple dead leaves at the bottom and I pinched them off.

Any idea what the spots could be from? I have been treating all my plants for fungus gnats because I saw a gnat flying around last week. I us 3% hydrogen peroxide and water in a spray bottle.