I have a maple that appeared to be in good health until last week.
The leaves are deteriorating at the tips. I've snipped some and left the
branches. I soak it 3 times a week for 5 minutes. It has decent early AM sun.
BRBR

Why are you cutting off the leaves? It is probably not a disease & you are
defoliating the tree. don't do that until you know what you are doing.
Where do you live? Is your area hot or windy? You can't water bonsai on a time
schedule. At this time of year your tree should probably be watered every day.
Water from the top only, until it runs out the bottom.
Your maple is probably suffering from leaf scorch, a common problem but usually
only a cosmetic one. For the time being, put it in a slightly more sheltered
location. I have found the best solution to be regular use of Pro-TeKt. It
really works.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)