Amounts of vegetables in protocol

I am doing weight loss coaching after having lost my 15 lbs. Most of my clients have lost, but I have a couple whose weight won’t budge or even gain and are discouraged. They are in their first 6 weeks. They say they are watching their portions, no sugar or flour, one joy eat a week. I am wondering if they are eating too large a portion of vegetables. They eat 3 meals, no snacking, no intermittent fasting yet. Could you tell me how much would be a portion size for vegetables? I don’t see that in the Stop Overeating Workbook. Also, fat? 1 TBS per meal? Thank you!!