Canoeing and Brown Spots of leaf edges and tips.

They appear to be suffering from heat stress there is several cause that can be affecting your girl but it all comes down to that radio between heat humidity and light intensity but it's definitely showing signs of heat stress on the leaves even though your tent doesn't appear to be extremely hot at 28 degrees Celsius but also genetics is another factor to take them to play if you want to control this try to find a comfortable radio or bringing the light a little bit higher or introducing more fan air circulation something that can cool the tent down to avoid heat stress either way the plant is not going to die from it it's just going to struggle a little bit hope this information helps you out with your grown.