Jan's right, but the GOOD news is that the plaster curing will tend to raise your pH, so they may well balance each other out.
Just test your pH daily and your CYA weekly. Test your CH as well--your goal is a CH between 200 and 400, and you are at 150 now.

If CH keeps rising, I wouldn't worry, but if it falls consider adding calcium either as calcium flakes or as Cal-Hypo. The latter is sold as chlorine, but adds calcium.

WARNING: DO NOT MIX CAL-HYPO AND OTHER CHLORINE IN THE SKIMMER OR IN CHLORINE FEEDERS! VERY DANGEROUS! However, adding Cal-Hypo powder directly to the pool water is perfectly safe.

Carl