It sounds like you already know the likely problem. Stop watering and maybe replace soil, and also relocate in a location with much more light. However, direct sun now, if your plants are indoors, might burn them, so be careful about direct sun.

These indestructables like heat and sun. Sun and heat. And did I mention sun? Heat will keep them growing but spindly. They love being outside during the summer months soaking up the sun but need about a week to adjust from indoors to shady outdoors to full sun. A cacti "like" fertilizer (low nitrogen) will keep the leaves shorter and wider and will encourage blooming. Greenish white flowers that smell like heaven and attract ants. I mix the fertilizer with the soil, when dividing or repotting, with sand and perlite.

They will also flower after a dry spell of 3 months, or in season to their species. I have some starting up now. The perfume is lovely, it will perfume the whole house. I don't get any ants however. CatiJoe, good advise for the UK , In the UK I would think clay pots would be the best, and not plastic, I seldom saw plastic pots in the UK. Norma