Save it for another cycle. The 200mg of decanoate in that blend will take a long time to reach peak plasma levels in your blood. About 6 weeks, just when you’re finishing up. While you’ll still have some of the same ester you’re already running between the 100mg of cyp and 100mg Enanthate, you will experience a decrease in test levels running 600mg of that compared to 600mg of the cyp you’re running, until the decanoate has had enough time to build up. At which point your cycle is over.

If your already running Cyp& have enough to Finnish up just use that. Stick you your cycle plan & try to avoid those “Frankenstein “ runs. If you’re running out of Cyp that’s a different story. Sounds like you’re eager to get into that Test-Blend400 while you already committed to the cyp cycle. Like bro said below me, it’s literally just changing the time release& frequency of injections for the most part. I’d finish up what you started& grab a few more PharmaQo Test-Blend400 for next time around, or use it for your cruise. That’s what’s great about test.
Hope you get the answer that you’re looking for. Stay safe& talk to the vets& guys who’ve been around here for a while. Like @irongame, @press1, @Glitch, and many many more.

You can do either man all the Esters are just different half lives so plan it out and you can do whichever it won't matter. You can use Test P to fill in the gap between the half lives as Test P is a shorter life and is needed about every other day. I personally however would just use up what you are using because I do not like to save a punctured vial until the next time I cycle as that increases the risk of infection or contamination.