One of the dimmers has a maximum of 300w (each gang) for incandescent lamps; when using LED's that reduces to 75w/gang. So for one of the gangs you are exceeding the limit.Sorry mate, what do you mean by re-rate them please?Tombola, according to both sets of Hamilton dimmer instructions, when you use either of these dimmers with LED's then you have to de-rate them by 75%.
And, as I said, Halers put a limit on the number of their lamps per gang - you exceed this on one of the gangs and possibly both.
So your Hamilton dimmer is not up to the job and should be binned for one that meets Halers criteria - phone or email them.

