Tenant not taking much care of property

Maintenance

I am disappointed in the way my tenant is taking care of the property and am writing to her about this. I have looked at the template letter and am unclear as to whether the statement about possibility of regaining vacant possession is too threatening or should go in so that there is forewarning in case I do feel it necessary to take that step in the near future.
I am going to itemise the main areas of concern in the letter. There is nothing horrendous but I feel there is a general lack of care such as not informing me that the shed roof felt had mostly come off in a storm and not attempting to make it weathertight, mouldy bath seals and not keeping the garden or front tidy.
I did have to write to her about the garden last year as a neighbour got in touch with me about it.
My tenant has lived in the house for 5 years now.