有關現在進行式既問題問問

9:00--9:50 am---washing dishes
9:50-9:55 am----break time between
9:55 am------washing again
The present perfect tense,though indicates an action took place in the past, is associated with the present idea of Now,
eg:-Tom has started washing (gerund) dishes at 9:00 am.
For an action just concluded when the second resulting state of washing is still present,
eg:-Tom has started washing dishes again at 9:55 am
From Mary, an arbitrary observer point of view, there are many ways to speak at the speaking time;
However, the present perfect continuous tense should be used.It is used to express the duration of an action up to the present,suggesting the (washing) action continuing at time of speaking=speaking time,The (washing) may continue into the future;
eg:-Tom has been washing dishes from 9:00--9;55,despite a break time between.

"Tom is washing dishes now."is correct when you say it on 9:55

At 9:55, Tom is washing dishes now.

Correct.

The TENSE is indeed correct....
but I think you need to add "THE" before the word "dishes".

There are many ways of saying this actually.
-Tom is washing the dishes now.
-Tom has just started washing the dishes again.
-Tom is doing the washing-up (now).

Hope this helps!

無問題 only if you answer a question of "what is Tom doing now?"

If you want to report the situation precisely as an observer, you have to say:

Tom has started washing the dishes again.