Reoccurrence Question

Hi ladies! DS was a MSPI baby and was on Elecare until he was one. We challenged with soy at 10 months and passed with flying colors. We then went to yogurt and foods with dairy as an ingredient at 11 months, and he was A-OK there as well. Switched to whole milk at a year and never looked back. It took forever to get him to eat solids because he had such a negative connection between food and pain, but in March he finally took the leap and has been loving life and eating everything and anything. Until now. He's 17 months now and mucus showed up. He is getting 4 molars and 2 canines at the moment. We have an appt with the GI because we promised to go back at the first sign of blood or mucus in the future, but curious if anyone else has been through this. Anyone else have months and months of no symptoms and then they came back? I have friends that claim their baby's poop had mucus during bad teething but with his history I don't want to ignore it. If anyone can give me any hope at all that they're not going to put him on the elimination diet next week, I'd take that silver of hope...It will be so frustrating to limit his great eating. (obviously we'd do it if we had to, though!)