Hen is not acting normal self.

[Drew3]

My hen has been acting strange since the 4th of July. We thought maybe the fireworks threw her off, she was isolating from the rest of the group but when we went over to her she ran back over to them. I sprayed some Vetrx in the coop that night and she seemed better the next day. I sprayed more that night and on the 6th she was isolating again. She was eating, comb full, just not roaming the property with the others. Yesterday, she was walking in and out of the coop, sitting in the shade (it's been very hot all week) and I kept giving ice in their water and fresh water. I added Nutridrench in a separate bowl for her and she wasn't interested. Yesterday was the first day she didn't really seem interested. But she was running when we walked near her but then seemed out of breath and very hot. Mouth open and panting. I cooled the ground down by spraying it in an effort to keep her cool and then we noticed another hen had worms. The hen with worms is still laying-the one in question stopped almost a week ago. We treated them all with a low dose of ivermectine (we know how toxic it can be in high doses) and this morning she is stumbling and the others are fine. I don't know what to do! Any advice is appreciated, I really don't want to lose her.