It is impossible to determine from the example if the words are countable or uncountable. There is no grammatical clue or difference in meaning.
Would it be possible to use a plural in these sentences? Yes (but perhaps odd) Imagine a person whose weight went up and down:
My weights are 150lb in the morning and 155lb in the evening.
Or a runner with different speeds:
The runner's speeds are 6km/hr at a jog but 12km/hr when sprinting.
So in principle, both these could be countable. But these are very odd, artificial constructions.
You can't tell just from the structure if a word is countable or not. Consider:
My cat is white.
My rice is white.
But rice, you know, is uncountable, whereas cat is countable.
But "coffee" you know can be both countable "a coffee" and non-count. So tell me, which one is it:
My coffee is white.
I say you can't tell, and it doesn't matter.