Sounds like detox, which means Chlorella is doing its thing. That's good. You can go through it by continuing at your current dose and take something to ease the symptoms, or scale back your dosage and ease your way back up according to what your body can handle. No matter what, you should drink plenty of water.
With regards to the Vitamin Shoppe brand, I ran low on my regular Earthrise brand and purchased Vitamin Shoppe Super Chlorella as a stand in, and I began to detox all over again! I have been on it since January and reached 12g quickly where I have been holding since the recent change, it shocked me and sent me researching this "Super" Chlorella, I have not found the answers yet, but to send me into detox made me think there is something with that word "Super". I am over the detox symptoms, it was brief.
If you can hang, do so- like a previous poster stated this too shall pass. I am doing wonderful, and one of those able to take both Chl/Spr. I am GREEN for life.
You can always seek the help of the wonderful ladies within the Chlorella thread, there are several that have had success from the start of the thread and will be more than happy to offer advice to help you along. Best wishes to you.