If you're in veg, neem oil is much better than citric acid for powdery mildew. It will both kill and prevent PM.Imo, Yes, you should be worried, and vigilant. Those conditions can create havoc very quickly if the wrong spore lands in the right place. Bear in mind flower means less time with the light on which means cool damp and dark, perfect mold conditions.
Your plants are very healthy and the stronger the better but flowering brings new demands and stresses so things can get out of hand - tbh with all that lush foliage, I might be tempted to pre-treat with @InTheShed 's citric acid treatment if you can get (or have) the stuff.
This is a link to the post with the info:
Thrips
You are introducing a fungus to cure a mildew problem?? What is the name of this fungus? Or, did you mean that you are getting a 'fungicide' which is a totally different thing. Its a bio fungicide called aq 10www.420magazine.com
Once there are pistils I switch to citric acid, but at a much reduced strength than that link. Go with .25% rather than 1%.