Q.pruning/changing color of hydrangea
I have 4 hydrangeas. I water them weekly with diluted aluminum sulfate. Many are blue and some are pink and purple. Should I be putting this solution a foot around each bush? I pour it down the center but are roots a foot apart from center. I use a gallon of water and 1 tbs of sulfate for each plant, so should I add more solution to non plant areas to get roots all over saturated with diluted aluminum? Should I increase to 2nd for each gallon to make solution a little stronger? Also, some bushes have 3 tall stalks and the rest if the bush is low. Should I cut this stalks down? One bush has very few blooms on it right in between my other bushes which have tons of blooms. I don’t know why I don’t have the same amount on this one bush? It was and is treated the dame as all the others.

You can water the entire drip line of the plants with your fertilizer. I would not increase your ratio.
I am listing a few links for you, including pruning information.
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/prune-hydrangea-bushes-hydrangea-pruning-instructions.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/change-hydrangea-color.htm