Well, this is one of those general kind of things that could be caused by many things and everything: drainage issues (too much water accumulating and not draining out), drought, sunscald, etc. Thinking about general things, start by checking that draining holes are not obstructed. I noticed that that there is no mulch so add 3-4" so the moisture will not evaporate quickly and you will not need to water often. Wind protection in windy areas also helps. Also, you do not display where are you located so make sure those 6 hours of sun are morning sun until 11am-ish. Too much sun can cause sun damage but it looks different than yours. Check the soil pH to make sure it is acidic (although they tolerate some alkalinity before showing symptoms of high soil pH). I did not notice those round fertilizer pellets so I assume you are providing minerals via some liquid fertilizer; just checking on that as that would not necessarily cause brown leaf tips. Some mineral deficiencies might cause problems but I assume the plant is getting at least a little of minerals.