Hope someone can help, I've been keeping cactus for a couple of years now with no problems. My parents potted me a terrarium for Christmas-i lost one cactus very quickly (and removed it) but the other two grew quickly and thrived- now however they are going sickly yellow and soft!
I love my cacti and succulents and want them to thrive, they don't get the most heat as I live in the chilly north west of the UK but that's never been a problem before now.
I mist all my succulents and cacti once a month or so.
Also, how would you recommend I repot the bigger cactus, and what is the white stuff on the roundy one? I've removed it gently with a paintbrush before but not sure if it's supposed to be there...