Non-attachment is a principle of living in the moment. If we live in bliss all of the time, how will we come to appreciate it when it arrives?

Do you practice any sport or martial art?

one thing springs to mind: hormones. (excuse my spelling errors, english is not my first language)

While you were taking your vitamins your body finally repleneshed all its deficiencies.
With this it was able to once again manufacture all the hormones it needs. Think of growth hormone, aldosterone, cortisol, testosterone etcetera. Some of these can give you a buzz like the one you describe.

For example, progesteron calms you down and makes you feel enlightened. Also enhances your sensitivity. Both men and women produce progesteron. In a man, it is the adrenal gland making progesteron. Progesteron competes with cortisol (the stress-hormone) for the building blocks. (these are the hormone pregneleneone which is made from cholesterol).
So, if you are stressed out or do not eat enough of the right fats, you will not produce enough progesteron. Your body will favour making cortisol over progesteron because cortisol will save your life from the tiger your body believes is attacking you. Also, in out modern life, adrenal glands are usually tired, what with all the stress and coffee and cola and sugar and junkfood that is joilting our bodies all the time.

So there you were: eating healthy, taking vitamins and nourishing your body (and your adrenal glands). You recovered remarkably and your body 'overdid' it a bit leading to euphoria.
You can imagine that your bodycells might well be very sensitive to the hormones you were producing because before you produced very little of them and they had to really pay attention to get them. Suddenly there was an abundace, with you eating all the good stuff. Leading to euphoria.
Now your cells have restored to normal sensetivity and your happy cloud has gradually weared off.

Another hormone that could be involved with this kind of euphoria is DHEA. Or growth hormone.

I can tell you at least that the omega 3 and the B12 and vit. C all boost the cells in all your body in a marvelous way and especially the celsl of the adrenal glands thrive on them. The fish-oil is the right kind of fat, it is the kind that makes up all the membranes of all your bodycells. It makes them flexible. Contrary to transfats (found in all fried foods and margarine) which is a rigid kind of fat, making all your bodycells stiff and not able to function properly.
Vit. C is needed by your adrenals in large doses, 1000 mg is right.

If you want to know more you could look at the work of dr. Wilson who coined the term 'Adrenal Fatigue'. You seem to have followed the restorationprogram to the lettre