OP: you did not cite the specific relay bd you bought [a link would have been
helpful], but we'll assume the relays have reverse-diodes across the coils, so that's
probably not the problem.
Also, the digikey RC networks you linked don't look like what you want. I'd try
Doc's snubber ckt. However, you need to use robust R+C, not the usual tiny parts
found on typical bds. Eg, R should be 1/2 or 1 watt, and C should have a large
voltage rating, like 220VAC polyethylene or propropylene, metalized film part.