Likes acid conditions, so if you're watering with tap water, that might be the cause of this, really needs to be watered with rain water. If that's in short supply currently (it certainly is here in the south) water from coffee grounds (including some of the grounds) will do, or boiled and cooled down water. Responds better to tepid water too. When you repot, multi purpose will be okay as it should be neutral ph, but if you have ericaceous compost knocking about, that would be better - and wait for the flowers to pass before you do it. Does need a fair bit of watering, so I wouldn't think you're overdoing it, but make sure you don't leave it sitting in water in its tray or outer pot - empty any extra out an hour after you've watered.

i didn't realise it was on the ericaceous side. I just give it a squirt of Miracle grow every 10 days, but I'll use my ericaceous MG like I do with my rhods etc.

I'll think about getting it repotted once the flowers have passed.

Thanks