Small yellow/white spots on French Marigold seedlings

So for a bit of context, I planted some French marigold seeds into a 40 cell seed tray a couple weeks back and they’ve been growing quite well inside of my greenhouse with no issues. The weathers been pretty average here in South Wales with no extreme heat and no abnormal cold but in the last 2 weeks I’ve noticed they’ve started developing these small yellow-ish/white spots on their leaves and I’m not an experienced gardener so I have no idea what these spots indicate and if they can be treated but I’m sure someone on here might have some experience with this so all replies are very helpful 😁