Coal,Nuclear and Hydro plants

In my last games I noticed a weird counting of hammers
by these plants.They are all cumulative with a factory (50%),
but the results are (probably) not correct.

Some examples :

1) City with 22 hammers.Forge + factory -> 33 hammers,correct.
But with a coal plant the amount of hammers rise to 71 hammers.
And also with a Nuclear plant to 85 hammers.

2) Second city with also 22 hammers.Forge + factory -> 33 hammers.
But here there are 74 hammers with a coal plant.

So what's the deal with these plants?

Also the coal plant doesn't show 2 unhealthy icons in the city screen,
so the penalty is probably not there.

More info...
After loading the game again the visual amount of hammers is now correct,but
when a plant is build it is not.Also the real amount of hammers is still correct,so
only a visual problem.
The 2 unhealthy icons from the coal plant do appear in the health bar above the unhappiness bar.

One thing that affect the number of hammers : had a worker cut down a forrest recently ?

Otherwise, yepp, the Power system in general seems to need a bit patching!
In the game I end up choosing STEAM producing coal plants to power my cities, instead of electricity producing nuclearplants (or electricty producing coalplants) ! Why ? ->

The reason are several strange things :

(1) A steam producing powerplant gives me the same increase in productivity as one that produces electricity, so why rush for electricity when it isn't more useful then steam ?

(2) The Nuclear plants meltdown as often and terrible that you think they use blackpowder as moderator! So in fact they are very unhealty and do more damage then coal plants

The number of hammers shown may also be affected by:
1. Overspill from the previous build, if this is the first turn of production.
2. Bonuses from resources (stone, copper, etc.) for what's being produced; civics choices (Organized Religion); other buildings (Heroic Epic = +100% production for units). Probably others.