Bluey, re your peppers. It might be that as they are different varieties one is naturally better at setting fruit than the other. Chillies are sensitive to temperature extremes and some varieties drop their flowers if it gets too hot while others just get on with it. Some also take longer to mature (a bit like blokes) and fruit better once they've grown on a bit. The other thing I would consider is whether the 'sensitive' one is getting enough plant food - might need a bit more than the fruitful variety.
Failing that, I've always found a good stiff talking-to, illustrated with pictures of the compost heap, helps to concentrate their little leafy minds wonderfully......