As long as your not overfeeding the grow/bloom you will be fine to add it in buddy. It is best to have an EC meter though as its handy in these scenarios to let you know if your hitting them with to much feed.
Hey Mate,
It's hard to say if you do not provide any information about your grow.
Which brand of PK? What substrate are you using... and and and....
Good luck ✌️Oim.