ZZ Plant Spots on New Leaves

As the title suggests, on a couple of my ZZs, the newish leaves that they got last year seem to be going spotty and paler than they were previously.

I do not over water these plants, I have four ZZs and apart from these two, the others are perfectly fine.

Ive been watering them very infrequently due to the cooler temperatures over winter. I use minimal heating so I can’t see that they could be drying out.

Could it be pests?

It’s a shame cos these plants are awesome and quite large but the spots are really really unsightly.

Thanks.