It's for flowering. NPK ratio 1-2-5 is too little N for veg. Many people think there's no reason to increase P even in flower.
More K through the entire grow is beneficial. You can do that with inexpensive potassium sulfate, or Pro-Tekt silica in veg (most people refrain from using silica in flower. potassium sulfate would be good in flower.).
That looks like fish emulsion? I like to supplement a little in veg. It's good for the soil microbes. But, you have to be aware of the NPK ratio of your base nutrients, their strength, and use a proper amount.
(Didn't you post a photo of a yellowing plant yesterday? Fish emulsion would be good for that, if you use it correctly.).