Well, let Dr. Energon Skyblast take a look, eh?

: It appears that they're getting exposure to
something.What would your advice be, then?
Dr. Skyblast: Well, my advice would be to keep them not even in a container. Do you have some sort of darker area in your room or house? Place them there. Also, if they're standing in front of a window, either close the window or just take them away from there.
Could it be something in the house itself?
Dr. Skyblast: Possibly! Do you have a bug problem? If so, do you use bug spray frequently? What about air freshener? Are you a fan of Febreeze at all?
And of course, final say doc?
Dr. Skyblast: Well, my REAL advice would just be to keep the Transformers themselves in stasis lock in either the Ark or the Nemesis, respectively, but of course, you don't have that available. So, unfortunately, my primary advice would be to place them in a dark area, and keep them away from sun and pollutants.
Anything else?
Dr. Skyblast: Yes, as a matter of fact, there is. Would you mind telling us what area of the world you're located in? And if in the US, what area of the country? It could be something in your area, and, if so.... this could serve as a good warning to Transfans all across that area! Best of luck!