Sounds like oversaturated substrate, try to take a chunk of substrate and squeeze the excess water out.
Rosehair taranutlas should be kept more on the dry side with a waterdish, only exception are juvis and slings they need alot of moisture.
What works pretty good are mixtures of two different soils. Like Topsoil with crunched oak leaves (dry) or topsoil with ecoearth. Most of the ground dwelling tarantulas like to dig caves and topsoil has a good mixture of sand and earth, mixed up with a soil that stores water it is the perfect substrate.
Always check where your spider comes from, since there is a huge difference between tropical and dry habitats. Some of the south american spiders prefer a dry habitat like Brachypelma smithi, Brachypelma boehmi, Grammostola rosea,...
Lasiodora parahybana, Theraposa blondi are more on the wet side.