I've seen some posts where growers will keep the vegetative nutrient solution but flip the light to 12/12 for flowering for Week #1. Then in Week #2, they use the nute mix for flowering. I've always made a fresh reservoir of flowering nutes and flipped the lights to 12/12. Does anyone do anything differently?
in DWC I would not do that as nutes are way too important but in soils I do I reuse my soils, the only nutes added are late in flowering, so in fact Im putting my seedlings into 'hot" flowering nuted soils, that I dilute each with perlite it saves on having tons, yes tons of compost lying around
In coco, when I was running GH, I used a mix of veg and coco for 2-3 weeks and got great results. Makes sense, the first couple weeks during that super stretch they are building a lot of the same stuff they built in veg, but at the same time developing a hunger for flower nutes.
I don't know your situation but I might try leaving a bottle of water next to the nutes and leave for the same duration, feed the plants then drink the water, the logic being bad water taste may imply bad nutes good luck