Often cool nights below 50 degrees will induce early bud set, or you may have stressed the plants by allowing them to dryout too much after potting... You should pick off all the buds ASAP. Begin feeding them a constant 20-10-20 at 200 ppm and they should grow out of it. There is still plenty of time to salvage the crop...Bob.

Correct, and that's the answer I'd have given. Don't pinch. Disbud.

As for the having given the asters a pinch. Shouldn't hurt them.

Thank you so much!
Bob, what is "constant", by your standards? I fertilized them yesterday, and soaked them good. I am a wiz at regular perennials, but mums and asters are freaking me out for some reason lol.

deb, constant feed just means you fertilise with every watering.