Bridesmaid Dress Selection

Our Wedding is June 27, 2020 and I'm curious when other June/Spring brides are having their Bridal Party start selecting and ordering their dresses. We are going with Wine and Chianti for dress colors but not sure on style yet. The only issue I am running into is that one of my BM's just had gastric sleeve surgery in June and has already lost 60+ pounds. She will continue to lose weight (I'm so happy and proud of her) but it will be difficult to order her a dress too far in advance as she really has no idea what size she will be come June. I was thinking of going with a few at a time to look/order starting in December and January. This would give them ample time for ordering, exchanging (if needed) and alterations. I'm leaning now towards February/March to give my friend who had the surgery some more time to estimate her size. When are y'all ordering dresses and how soon are they coming in after placing the order? We are looking at David's Bridal as most of my maid's are out of town and it's easier.