I am not aware of the Wiltshire Horn or the Zwartbles being breeds that can breed year round - I think it's only the Dorset that can do that? Our Charollais certainly come into season a lot earlier than the local types but are not sexually active in the spring.
So I think it is highly unlikely, but you will want to be sure. And if it's not lambs, what is it?
BH double-checks for lambs as follows. Put ewe on her bottom, double her over a little (not too much), lean over her and feel her sides. There shouldn't be anything firm except a lamb. If you can't feel anything firm, you can push your fists into her stomach and check that she really is empty.
If the ewe has fluid coming out of her teats, then something is going on. Is the udder lovely and soft and pliable? Or hot, and/or hard?