All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
All the Ahaadeeth which you mentioned in the question are not authentic. As regards the Hadeeth about pomegranates, we have not come across it with the wording that you mentioned, but it was narrated with the following wording: “You should eat pomegranate with its pulp because it coats the stomach and there is no single seed of pomegranate that enters a person's stomach except that it enlightens his heart and repels the whispering of the devil for 40 days." This Hadeeth was narrated by Ibn ‘Adiyy among the Dha‘eef (weak) Ahaadeeth in his book entitled Al-Kaamil, and he ruled that it is fabricated.
As regards the Hadeeth about watermelon, then we have not come across it in the resource books of Sunnah that we have at hand, not even in the books that are compiled to contain Dha’eef Ahaadeeth. Indeed, the scholars stated that all the Ahaadeeth that are reported about the virtues of watermelon are Dha’eef. For instance, Ibn Al-Qayyim said in his book entitled Al-Manaar Al-Muneef: "Imaam Ahmad said that no Hadeeth is authentic about the virtues of watermelon except that the Prophet used to eat it."
With regard to the Hadeeth that you mentioned about milk, perhaps you meant the Hadeeth which reads: “Chew Libaan (a kind of gum), for it wipes away sadness from the heart as the finger wipes away sweat from the forehead. It strengthens the heart, augments the mind, increases the intelligence, polishes the sight, and expels forgetfulness." This was reported by Ali ibn ‘Arraaq Al-Kinaani, the author of Tanzeeh Ash-Sharee’ah Al-Marfoo’ah ‘an Al-Ahaadeeth Ash-Shanee’ah Al-Mawdhoo’ah, and he commented on it saying: "In its chain of narrators, there is Muhammad ibn Ibraaheem ibn ‘Amr ibn Yoosuf about whom Ibn Mandah said: “He narrated Munkar (rejected) Ahaadeeth."
Finally, we have not come across the Hadeeth with the wording “Mushroom is a cure for the eye.”, but there is a Hadeeth which reads: “The truffle is of Manna (i.e. it grows naturally without man's care) and its water is a healing for the eye.” [Al-Bukhari and Muslim]. The truffle is a known plant; it has neither leaves nor stem, and it grows in the earth without cultivation.
Allaah Knows best.