Looking at the ITF entry lists, the sisters are definitely moving up to 25Ks, they're down for 50K Minsk next week but I don't think they'll get in, but then they're down for a 25K in Poland the next week.
I realised that the sisters play really well in alternate patches. At the beginning of the year, it was Nadiya with her win at Nottingham and ITFs. and now, it is Lydua. But I guess its just due to luck of draws. Considering the fact that Arefyeva won one round in the MD as well, Nadiya did put up a good fight against her in qualies.