If the tips are truly dry, then it may need more water. But if the tips are more thin & whitish looking and not really brown, then it is probably too much water.
A way to see if your lawn is too dry is to walk on it. If the grass springs back up after it is stepped on, then you have plenty of moisture. If the grass blades break & stay flattened, that is a sign of dryness.
I suspect that your lawn is too wet. Zoysia is drought tolerant & only needs watered alot to establish itself over the first couple weeks.
As far as mowers, I like Honda. Excellent & dependable just like their cars. Also, a mulching mower is better so the nutrients in the cut grass are returned to feed the rest of the lawn.