It's only a 1% chance on the wishing wells, and 5% on the Crow's Nest. That is why people build diamond farm cities with as many wishing wells as they can pack in. If you have 100 wishing wells, the odds say you will get one diamond reward per day, but since it is random some days you get more, and some days you get none.
If you have only been playing a month and have one wishing well and one Crow's Nest, you likely won't see any diamonds for quite awhile yet, maybe months. Or maybe you'll score tomorrow. Long live the RNG