Hi
The older ones are Black Welsh Mountains. The younger two are half texel half BWM, and so far I’ve not seen them get matted coats.
If weather plays a part then that makes sense, we had the long warm dry patch in April, then the wet conditions in the last couple of weeks and it’s just since that started that I noticed the fleece get matted, but it must have been just over a few days.
If I put any fleeces into the washing machine my wife will literally kill me, even if it is to make beds for her cats! Although maybe an interesting new sideline, all natural cat beds, just need to find some buyers.