Fatsia japonica black spots

[beginner]

I have 2 large fatsia japonica in pots which are located under a pergola, they get the same amount of sunlight and water (about a pint once a week).
One of them has developed black spots on the leaves and many of the leaves and stems are turning brown and the whole plant appears drooped over.
My local garden centre recommended to spray with RoseClear and give them some MiracleGrow which I have done about a week ago.

The other plant seems fine however I notice some leaves at the bottom beginning to turn yellow and die.

Any suggestions as to the symptoms and what can be done ??

 

[cpp gardener]

I think they both need more water. When you water, you should have a good amount flowing out the bottom and I don’t think a pint will do that in that size pot. The affected one is in slightly more sun than the other and is showing symptoms faster because of that.