Managing pregnant horse with ticks

She's had another dose of ivermectin to kill the ticks and is on sulphur in her feed or supplements. I will also add apple cider vinegar to her supplements. I'm trying to avoid using chemicals on her.
There's less ticks on her and the ticks I'm picking off her are less active and some are actually dead. The invermectin has worked.
She is also improving with her skin infection since finishing her antibiotics.
Note her coat is a little darker- probably the copper and zinc in her supplements. The excess iron in Australian soil competes with copper and zinc, which causes coat colours to bleach, among other issues that are more important, like immune system, hair and hoof quality.