An idiom for "this was only a small part of"

In this sentence:

His deteriorating health, poverty and persecution by the authorities, all this was but a small part of the trials he had to endure in those years.

I wonder if there is any idiom that could liven this sentence. Looking on the internet I found the expression a drop in a bucket (Cambridge), meaning "small part of a bigger whole", but it doesn't really fit in my sentence and it is not very elegant either. I would need something more formal and it can be poetic, too. It must integrate well in the structure of the given sentence.

This was merely/just/but the tip of the iceberg.

The idiom tip of the iceberg basically means the small part of a much larger situation or problem that remains hidden. When only a part of something that can be easily observed, but not the rest of it, we say that the part is just the tip of the iceberg.

[MissouriStateEducation: Idiom]

• His deteriorating health, poverty and persecution by the authorities, all this was but the tip of the iceberg – there were many more trials that he had to endure in those years.