The uneaten caecotrophs may be caused by too many pellets - how much are you giving them?
All buns are different and different pellets will not always suit a particular bunny.
All of mine are fine on Science but I only give an egg cup per bunny each day - doesn't sound a lot but it's enough. They then eat more hay and that helps to prevent sticky bottoms. I have also started to give a few Allen and Page in with the Science as it has more fibre. They don't like it as much but it all gets eaten in the end because they know that's all they are going to get.
It could also be caused by too many veg - in particular greens.
Dependent on what amount you are feeding already, I would cut down slightly on the amount of pellets (but not stop altogether - this can cause a problem in it's self) and maybe change gradually what veg you are giving.
It is really important to check bottoms at least daily in this weather so I would really find a way to have a look. If your bunnies won't tolerate being picked up, is there any way you can sit on the floor and just lift their front legs of the ground leaving them grounded, or in the worst case scenario get them lying on the floor and look from the other end by lifting up their scut.
It's really worth finding a way that they will accept as flystrike is just waiting to happen in buns that have sticky bums.
Helen