Hard to give any sort of guess with so little info. Are they in a yard with pasture? Or do they just rely on hay and pellets?
It sounds to me like you've spotted some sign that subconsciously is setting off alarm bells in your head but you've not got the information to identify what you're seeing. In such a case I would recommend you get educated as soon as possible by reading a book or checking a site that has good descriptions of problems sheep can experience, and see if anything clicks.
Generally speaking, how are they looking? Pooping normally? Breathing normally? Not bloated? Resting, feeding, watering normally? When were they last wormed? Even the tiniest details can be symptomatic of something serious, or nothing, lol. Anyway, best wishes.
I think they are ok now

Also sorry I didn't ask sooner but can I join this thread?