I'd say that's about right.

What I've noticed during my current grow is that under LEDs, the plants will show deficiencies, particularly with Mg, but also the other macro nutes, right after you flip if they don't have the right nutrition. Then they show light stress a lot more.

I'm running 4 clones of the same LED-sensitive plant. One got a store-bought mix called Coast of Maine, the other three got FFOF. CoM is twice the price and I've never heard of it before, but I figured this was for weed bro science, so the expenditure was worth it.

The CoM plant is a darker green, two of the other three FFOF plants show Mg deficiency, the third is a light green, just a hair away from showing a deficiency. Now, the CoM plant is doing fine, while the other three show light stress.

So, bottom line, at around 20 days, I'd supplement with some epsom salts dissolved in your water and keep them on veg nutes for at least a week into flower, if you're using LEDs.