During the problem times of Airfix, who were then owned by Humbrol, as part of a Group, the Humbrol company went bust. The factory at Kingston upon Hull closed down, and was destroyed by fire a few years later, after lying derelict. So, the paint is obviously made elsewhere now, but to a much lower quality. As for lead content, this had already been addressed in the 1970s, long before other countries got on 'the band wagon' and, even with further Health and Safety considerations, the Humbrol paints were still of high quality, consistently.
If other companies can produce high-quality paints, with consistency in colour, shade and quality, then there is no reason this can not be done for the Humbrol brand - unless it's being produced by some second-rate outfit, as a cost cutting exercise. If that's the case, then the long term result will be the disappearance of Humbrol as a paint brand.