| | Re: No newts in water...for MONTHS
If water quality is ok, temperature is ok and the animal is not subject to an stressful environment, then my guess would be the filter, too.
If the kind of plants you have are surface floating ones, those wonīt really help. You need submerged plants that reach the surface and offer them a place to partially support their weight while in the water. You shouldnīt be afraid of going filterless if you have a large amount of plants, itīs entirely redundant.
If substrate is an issue because of the blackworms, my suggestion would be to go bare-bottom. Itīs arguably a less aesthetic option (although it sort of grows on you, i find xD) but itīs the most practical.
Anyway, if youīve only had them from september, itīs possible that they are still experiencing the effects of the severe stress they suffered. It can affect them for quite a while but if conditions are good, they will eventually snap out of it.