Son’s quick changes in symptoms on Stelara

My son started Stelara in January:
01/25 loading dose
02/27 calpro < 50
(Normal bowel movement from around the 3rd week after the injection until this point)
03/20 bad diarrhea
03/22 -Stelara 8th week injection, crp normal, sed rate is bordering around the high range-
03/28 bad diarrhea
04/01 awful diarrhea
04/05 accident in the underwear + bad diarrhea
He also dropped 3 lbs from last week.
It is 04/05. I’ve enjoyed about 5 weeks of…