I planted some ES hydrangeas this spring as well and some of them have already run their course as well for me. Pictures are always a good thing when describing what youre talking about on here so if you have the capability to take photos please do so.

As for removing spent flowers you certainly are able to do so and it will promote new buds to form. Leave the white/light green flowers alone but ones which are brown you can deadhead. You can cut from where the blossom was down to the first pair of leaves you see. Good luck!