Rabbi, You said that in the the new converts only celebrate one day of sheva brachas. Is this because they were previously "married" before converting, or is this something to do with them being converts, and the same p’sak would apply if a natural born Jew married a convert? Please can you explain the reasoning, and source

ב"ה Shalom The Rabbi whose answer you referred to followed the position that in the case of a convert woman only one day of Sheva Brachot is kept. The reason is because that is not considered a new marriage which warrant 7 days. The same is the case if a widow married a widower. (See Shulchan Aruch Even Haezer 62:6 and commentaries ad. loc.) All the best.