I just cleaned all the leaves with water as it was dusty, might have been ‘brushed’ but many are doing the same so they can’t all be getting brushed on every side? Thinking it might be either the soil or perhaps humidity ?

It's winter, and the air is dry; the leaves are drying out. Raise the humidity in the house (more watering won't help and could lead to root rot).

Tatts how would i do that ?

You raise humidity with a humidifier, and in my house that is all that has really made any difference.

Setting the plant upon a large tray with rocks and then water (that never touches the bottom of the potted plant) is often recommended. I have not had that give much relief. Misting is recommended by some and not by others. It can lead to disease if the plants are damp and don't dry out before night time. But some say it's worked for them. The plant you have requires high humidity. You can buy a hygrometer at Lowe's or some such big box store to get an idea of the humidity level where the plant is, they are not expensive. Once you now how close or far off hour humidity is, you could make decision after that. A bathroom or kitchen are often the best rooms for humidity.

Brown tips can be a sign of overfertilizing.

Symptoms and signs of over-fertilization:

• Crust of fertilizer on soil surface.
• Yellowing and wilting of lower leaves.
• Browning leaf tips and margins.
• Browned or blackened limp roots.
• Defoliation.
• Very slow or no growth.
• Death of seedlings.

Over-Fertilization of Potted Plants - Penn State Extension

Pennsylvania State University › extension › ...

Dark leaf plants like that don't need full sun. They are shade plants when they are grown outdoors.