Young leaves are very small in size and spots on leaves

We planted Mango plants in Sep this year and last week I noticed 2 issue in some of the plants: 1. Small leaves: The young tender leaves are very small in size. Is this normal or is there any disease / disorder, which results in small leaves. 2. Dark spots: Few plants have dark spots on the leaves and the leaves are drying at the border. Would appreciate any help / solution, on the above issues.