Has your LO suddenly developed aversion to formula over breastmilk?

My LO suddenly has developed an aversion to HiPP HA after having breastmilk. He started daycare 1 month ago and is continually congested and had diarrhea and then green poop for the last 2 weeks. All tests for bacteria, parasite and viruses are negative. Does anyone else have any experience like this? His congestion seems to be worse and worse and so is his eczema on his stomach. I am not sure if something has hidden soy or he has suddenly become intolerant to the formula, since he is having more of it in daycare.