People whose health (has taken / takes) a turn
tofor the worse should not drink.
Personally I think it is more suitable to use 'has taken' because this means that the people are ill or unhealthy now, so they need to go to the doctor and get medicine, not to drink. However if I used 'takes', it would be awkward and I don't know why.
If I used 'takes', what happens?
people who (are feeling / feel) slightly under the weather with a cold should not drink.
I think both of them are right. because present tense can describe the idea that an action is happening now and present continuous tense can also deliver that meaning too.
Are there any subtle differences between 'are feeling' and 'feel' in this sentence?