How do you say when it seems like “already gone bad”
We can say when we saw the food has rotten “The food has gone bad”
But how can I say when it is not definitely gone bad ? When I think “it has gone bad”

Is that below grammatically correct?
“It seems like gone bad”or “it seems to be gone bad”?
How can I say with”seem”

Question

How do you say when it seems like “already gone bad”
We can say when we saw the food has rotten “The food has gone bad”
But how can I say when it is not definitely gone bad ? When I think “it has gone bad”

Is that below grammatically correct?
“It seems like gone bad”or “it seems to be gone bad”?
How can I say with”seem”

Answer

When food looks slightly beyond the eating stage, you could say, "This seems to have gone bad".
For food, such as bread, that is dry, you can say, "This seems stale".
With fruits or vegetables, you can say, "These are not fresh" or "These don't seem fresh to me".
If you notice an unpleasant smell, you can you, "This food seems to be rancid". 
Some people also use the expression, spoiled.
For example, you could say, "This milk has spoiled".

Answer

Along with the other great response by Naomi, I would add:
gone bad=turned 
Example: Don’t dink the milk. It has already turned.