How do I (47/M) tell my ex (34/F) to not get angry at our kid for eating meat at my house?

TL;DR: My ex is screaming at my kid for eating meat at my house; want advice on how to request she stops doing this.My ex and I (47/M) separated about four years ago and we share custody of a seven-years-old kid; she is vegetarian and into organic food and I'm not. I usually accommodate my kid preferences regarding certain foods if he likes the organic brand better, but regarding a vegetarian diet the research I've made seems to indicate that for small kids an expert (such as a nutritionist) need to be involved to ensure that the kid is getting all the nutrients he needs at this stage of his growth.Things came to a head during my kid last annual checkup, when we found out that he only gained half a pound from a year before; when I pointed this out to the pediatrician her eyes widened and she said that although not unheard of we need to pay attention to his weight and that she would be more concerned if something like that happened on his next check up.I've been trying to talk to my ex about this, but our parenting agreement indicates that all our communication has to be by email (she insisted on this) and she's not very forthcoming about this or any other matter; I would ask her if she relied on a nutritionist advice when choosing our son's diet and she simply ignores the question or change the topic. When my son is with me, I don't follow a vegetarian diet and he eats meat (mainly chicken and beef or turkey sausages).Today my son refused to eat his sausages because he said that "mom would get angry at me if I do that"; I respected that and explained to him that over this matter his mom and I have a difference of opinion and that there's nothing wrong with eating meat. He told me in his own words the uneasiness of being trap between our conflicting view on this matter.This is a matter of great concern to me as I don't want my son to suffer due to an inappropriate diet; I'm open minded and I wouldn't mind a medically supervised vegetarian diet if my son receives the necessary nutrients for a healthy growth. But my ex refuses to discuss this matter. As we are required by our parenting agreement to discuss these matters in good faith, I would like your advice in how to approach this with her. via /r/Parenting https://ift.tt/2VsxSH0