I wouldn't use vitamin powder or drops that dissolve in water because of 1) quality/freshness and 2) bacterial growth. I guarantee you're going to bump into a lot of bacterial growth problems if you put vitamins in her water and don't change it frequently (you should do this anyways, but you know ). I used to breed Budgerigars and this is a brief list of what I fed them during breeding season:
Approximately...
50% Pellets
30% Seeds
15% Fresh vegetables
5% Fresh fruits

Cuttlefish bone and mineral blocks are always available and frequently replenished. Additionally, I had a bowl of supplements that they loved to nibble on every now and then. I don't quite remember the exact measurements, but I believe it was composed of a heaping tablespoon of storebought egg powder (I can't seem to find a link, but you should be able to find it in a PetSmart or PetCo), a heaping tablespoon of crushed ZuPreem pellets, and one last tablespoon of crushed Roudybush pellets, all mixed together into a fine powder. I used a mortar and pestle to crush the pellets. You can also substitute with a tablespoon of crushed Harrison or KayTee pellets.

When my hen was laying, I had to up the calcium even more, so every other day, I would hang a bunch of parsley from the ceiling of the cage and make a little "bok choy bush"

You should try to incorporate fresh, dark, leafy veggies into Spike's diet like kale, bok choy, and even carrot tops. Anything dark and leafy is perfect Be aware of spinach, however, as too much of it can block calcium absorption. Good Luck!