"Ram horning" is a common symptom of excess nitrogen.
In response to too much nitrogen, a cannabis plant's fan leaves will cup and turn downwards like a ram's horn.
This tends to happen relatively quickly after feeding. The best remedy is to flush plants three times with plain water and revisit the fertilizer program.
The fertilizer recipe and strength may be acceptable; some cannabis varieties are simply more sensitive to moderate nitrogen levels than others.
If you are growing a variety that easily reacts this way, be prepared to use two different fertilizers.