Grout for outdoor tiles with small gap between slabs

[xyz123]

Hi, looking for some advise pls. I made the mistake of getting some cowboys lay our patio last year. The slabs are porcelain tiles suitable for outdoor use. The gap between slabs is small maybe 2/3mm. Builders used silkafix fast fix but I didn't rrelise at the time that it is for larger gaps and not 2/3mm. So it didn't cover properly and there are some small gaps in grout. I am trying to do a temporary fix short of removing and regrouting everything again. Is there any recommendations for a product suitable for small gaps between slabs.

Thanks.